This is a bit indirect, but since homebrew always boots in a European environment the framerate depends on the bPAL60 flag, which is always auto turned off if bNTSC is set to true as of 2e5e724f94. By actually indicating that we're PAL on homebrew boot, the rest just falls into place.
NTSC GameCubes have no Language setting, so the language byte in SRAM is always 0. Some NTSC games do react oddly and display unfinished translations and similar when the byte is set to a nonzero value that corresponds to a non-English language on a PAL GameCube. See issue 7731: https://code.google.com/p/dolphin-emu/issues/detail?id=7731.
This fixes a minor bug where the IPL thinks the SRAM has been corrupted and forces you to re-set date/time and settings when you change language in Config -> GameCube while not skipping the IPL on boot.