autofdo.txt empty

I've followed the instructions here on my Android 12 device:
https://android.googlesource.com/platform/system/extras/+/master/simpleperf/doc/collect_etm_data_for_autofdo.md

However, when running:
```
# simpleperf record -e cs-etm -a -d 1
# simpleperf inject -i perf.data --output autofdo -o autofdo.txt
```
The resulting autofdo.txt is completely empty. This was all done on device. Trying to get an intermediate branch list results in:
```
# simpleperf inject --output branch-list -o branch_list.data
simpleperf I cmd_inject.cpp:495] Skip empty output file.
```
The simpleperf version I'm using:
```
# simpleperf --version
simpleperf I command.cpp:257] Simpleperf version 1.build.eng.mosfet.20221102.163902
```

Any idea what could be going on?