If he gets the alloys machined less 5mm the longer wheel bolts supplied with the alloys may not fit that's why i said the one's he has on the car at the moment which are shorter should fit fine.
You are missing the point about the seats...
OEM bolts are RADIUS seat.
Aftermarket BBS are 60 degree TAPER seat.
You cannot use RADIUS seat bolts on TAPER seat wheels or the other way round as it's unsafe and you risk your wheels falling off.
You NEED to match seat type with bolt type...and his OEM bolts have the WRONG profile for aftermarket BBS wheels.
So fit, as it screw in and not hit the ABS ring, yes.
Be safe...no. Utterly wrong...and potentially dangerous.