This does not change the original LED function as such ...
But as the floppy light stays on even while the hard drive is accessed (yellow) , the firmware should actually turn off the yellow LED and light up the green one only... So this will bypass what the ST is doing but only when the hard drive is accessed where the green LED takes priority and lights up without the yellow LED on.
The bottom line is, the floppy drive will always flash yellow as normal, and the hard drive will always flash green when accessed.
No idea, I don't really consider any other machines other than the STFM