Cannot install 2 versions of swift on windows

See some weird behaviour when installing 2 versions of swift on Windows

Steps To Reproduce:
While trying to verify the vscode-swift extension, I had installed Swift 5.10 using exe downloaded from https://www.swift.org/download/

Swift —version worked fine:
C:\Users\award999\AppData\Local\Programs\Swift\Toolchains\5.10.0+Asserts\usr\bin\swift --version
Swift version 5.10 (swift-5.10-RELEASE)
Target: x86_64-unknown-windows-msvc

Now installed latest 6.0 snapshot

Now none of the 5.10 command line tools work, i.e. no output and seemingly just exit when spawned, but 6.0 is fine:
C:\Users\award999\AppData\Local\Programs\Swift\Toolchains\6.0.0+Asserts\usr\bin\swift --version
Swift version 6.0-dev (LLVM e878388283d7b73, Swift eb92e6e50035d21)
Target: x86_64-unknown-windows-msvc

On uninstall of swift 6.0, 5.10 starts working again. Not sure how common it is to have 2 toolchains but seems odd.