@Aurimas the intention (and the actual behaviour AFAIK) is that the speed factor (M220):
is applied to the F parameter in G0/1/2/3 moves
does not affect anything else
is not applied to commands in system macro files (homing files, pause/resume files, start.g, stop.g etc.)
does not override or change the M203 machine limits (i.e. the speeds of moves will still be limited by the M203 parameters).