Oops, I was wrong about the second case. It installs the old version of GCC by default regardless of whether I have framework = arduino enabled or not, and if the old version is installed, it defaults to using that unless I have framework = arduino enabled. But I was able to fix that by adding this to platformio.ini:
platform_packages = platformio/toolchain-atmelavr@^3.70300.220127
Sorry for the confusion, I was trying a bunch of things and I lost track of what I did when.
Anyway, I have a decent workaround now, but why is it defaulting to installing the old version to begin with?