why 680m vbios for p150hm is working in p150em??

hi guys

i have a simple question.

i have p150em clevo with 680m 4gb with version 29

and yesterday someone asked me to sell the vga card for p150hm.

then, i googled some info about flashing the 680m vbios for 150hm

then, i realize that only the 29 version will work in p150hm.

however, i caanot understand why this version worked both in 150em and 150hm.

in case of 7970m , we should flash the vbios to disable the enduro system bcuz p150hm is nonenduro and

nonoptiomus model.

but...

why 680m vbios for p150hm is working in p150em??