Looking at the available toolchain-gccarmnoneeabi versions at bintray the registry, there is version 1.90201.191206.tar.gz implying GCC 9.2.1. By using the documented platform_packages (docs) directive, you can use it in your project as
platform_packages =
toolchain-gccarmnoneeabi @ 1.90201.191206
The thing with updating toolchains by default is not that easy, as to provide the maximum compatibility with how the original frameworks are compiled. E.g., Arduino (avr) was compiled for a long time with a GCC 5 version, and PIO did the same, to maintain compatibility and not break the code.