IIRC, some of the extra ROM storage includes what we've assumed to be repeated copies of the same ROM.

If so, could some be copies of earlier ROMs with the proper startup sound for, in this case, the IIci? :?:

Is there anything in the Inside Macintosh startup procedure documentation that indicates that a CPU might look for a machine ID indication (bus multiplier type resistor array?) or poll the system for Mac specific ASICs before banging on one particular ROM image's door?

Dunno, just spitballing! :-/