An interesting question would be: if you check the Gestalt ID of a 512ke after installing a Dove MacSnap SCSI or other compatible-with-the-Apple-drivers card does the ID then change to that of a Plus?
Anyway, it seems like sort of a moot consideration. Whether or not the Gestalt ID matches a Plus after installing upgrade XYZ in a 512ke it's still readily identifiable as being "not a Plus" physically even without cracking the case. (It's still a different motherboard with no SCSI connector and 9 pin serial ports instead of Mini-DIN.) The only upgrade that "ruins it" is a Plus motherboard/bucket swap.