You’re explicitly selecting an older >5.0.0 compiler here? Pretty sure that’ll give you a 1.50401.210106 version, aka 5.4.1.
Have you tried
platform_packages =
toolchain-gccarmnoneeabi@~1.90301.0
to grab a 9.3.1 toolchain? (per https://api.registry.platformio.org/v3/packages/platformio/tool/toolchain-gccarmnoneeabi)