extra_script global defines not working

I am trying to add a global define to a project build extrascript like this:

global_env = DefaultEnvironment()
global_env.Append(CPPDEFINES=[("USBCON", 1),("HAL_PCD_MODULE_ENABLED",1),'USBCON'])
global_env.Append(CCFLAGS=["-D USBCON"])
print("<<<<<GLOBAL ENV DEFINES>>>>>")
print(global_env.get('CPPDEFINES'))
print("<<<<<GLOBAL ENV FLAGS>>>>>")
print(global_env.get('CCFLAGS'))

as per the example here: https://docs.platformio.org/en/latest/manifests/library-json/fields/build/extrascript.html

But defines and flags are not added, if i verbose build they are present in the log, but not present in the build command, build output:

CONFIGURATION: https://docs.platformio.org/page/boards/ststm32/genericSTM32F401CD.html
PLATFORM: ST STM32 (19.1.0) > STM32F401CD (96k RAM. 384k Flash)
HARDWARE: STM32F401CDU6 84MHz, 96KB RAM, 384KB Flash
DEBUG: Current (stlink) External (blackmagic, jlink, stlink)
PACKAGES:
 - framework-arduinoststm32 @ 4.21001.0 (2.10.1)
 - framework-cmsis @ 2.50900.0 (5.9.0)
 - toolchain-gccarmnoneeabi @ 1.120301.0 (12.3.1)
LDF: Library Dependency Finder -> https://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
<<<<<GLOBAL ENV DEFINES>>>>>
deque([('PLATFORMIO', 60118), 'STM32F4', 'STM32F401xE', 'STM32F4xx', ('USBD_VID', '0x05f3'), ('USBD_PID', '0x00D2'), ('USB_MANUFACTURER_STRING', 'STR(RailDriver)'), ('USB_PRODUCT_STRING', 'STR(RailDriver)'), 'STM32F4xx', ('ARDUINO', 10808), 'ARDUINO_ARCH_STM32', 'NDEBUG', 'ARDUINO_GENERIC_F401CDUX', ('BOARD_NAME', '\\"GENERIC_F401CDUX\\"'), 'HAL_UART_MODULE_ENABLED', 'USE_HAL_DRIVER', 'USE_FULL_LL_DRIVER', ('VARIANT_H', '\\"variant_generic.h\\"'), ('VECT_TAB_OFFSET', '0x0'), ('USBCON', 1), ('HAL_PCD_MODULE_ENABLED', 1), 'USBCON'])
<<<<<GLOBAL ENV FLAGS>>>>>
-mcpu=cortex-m4 -mthumb -mfpu=fpv4-sp-d16 -mfloat-abi=hard -Os -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -D USBCON
Found 15 compatible libraries
Scanning dependencies...
Dependency Graph
|-- USBLibrarySTM32 @ 0.3.0 (License: LGPL-3.0-or-later, Path: D:\Source\GitHub\USBLibrarySTM32\examples\SerialUSB\.pio\libdeps\bluepill_f401\USBLibrarySTM32)
Building in release mode
arm-none-eabi-g++ -o .pio\build\bluepill_f401\src\main.cpp.o -c -std=gnu++17 -fno-threadsafe-statics -fno-rtti -fno-exceptions -fno-use-cxa-atexit -mcpu=cortex-m4 -mthumb -mfpu=fpv4-sp-d16 -mfloat-abi=hard -Os -ffunction-sections -fdata-sections -nostdlib --param max-inline-insns-single=500 -DPLATFORMIO=60118 -DSTM32F4 -DSTM32F401xE -DSTM32F4xx -DUSBD_VID=0x05f3 -DUSBD_PID=0x00D2 -DUSB_MANUFACTURER_STRING=STR(RailDriver) -DUSB_PRODUCT_STRING=STR(RailDriver) -DSTM32F4xx -DARDUINO=10808 -DARDUINO_ARCH_STM32 -DNDEBUG -DARDUINO_GENERIC_F401CDUX -DBOARD_NAME=\"GENERIC_F401CDUX\" -DHAL_UART_MODULE_ENABLED -DUSE_HAL_DRIVER -DUSE_FULL_LL_DRIVER -DVARIANT_H=\"variant_generic.h\" -DVECT_TAB_OFFSET=0x0 -Iinclude -Isrc -I.pio\libdeps\bluepill_f401\USBLibrarySTM32\include -I.pio\libdeps\bluepill_f401\USBLibrarySTM32\src -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\cores\arduino\avr -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\cores\arduino\stm32 -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\libraries\SrcWrapper\inc -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\libraries\SrcWrapper\inc\LL -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\libraries\USBDevice\inc -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\libraries\VirtIO\inc -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Drivers\STM32F4xx_HAL_Driver\Inc -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Drivers\STM32F4xx_HAL_Driver\Src -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\STM32F4xx -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\ST\STM32_USB_Device_Library\Core\Inc -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\ST\STM32_USB_Device_Library\Core\Src -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\OpenAMP -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\OpenAMP\open-amp\lib\include -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\OpenAMP\libmetal\lib\include -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Middlewares\OpenAMP\virtual_driver -IC:\Users\Levi\.platformio\packages\framework-cmsis\CMSIS\Core\Include -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Drivers\CMSIS\Device\ST\STM32F4xx\Include -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\system\Drivers\CMSIS\Device\ST\STM32F4xx\Source\Templates\gcc -IC:\Users\Levi\.platformio\packages\framework-cmsis\CMSIS\DSP\Include -IC:\Users\Levi\.platformio\packages\framework-cmsis\CMSIS\DSP\PrivateInclude -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\cores\arduino -IC:\Users\Levi\.platformio\packages\framework-arduinoststm32\variants\STM32F4xx\F401CC(F-U-Y)_F401C(B-D-E)(U-Y) src\main.cpp
(then the build fails cause the defines are missing)

Am i missing something? I followed the example almost literally but neither the flags or the defines are showing up?

Start with the extra_script example linked in the issue and reproduce the STM32F401CD build using the shown DefaultEnvironment, CPPDEFINES, and CCFLAGS values. Compare the printed environment with the verbose compiler command; done means the requested defines and flags appear in that command and the build no longer fails because they are missing.