So the other person (who does not have the same surname) can sign for room service, etc.
Or is that very 1990's hotel systems??
I've never been challenged on anything I've signed to my room. Not sure if that's good or bad, but sometimes my partner will just write my surname anyway. I truly don't know if they check the signature. It's probably mainly there for dispute resolution I'd guess.
I just feel its not worth complicating the booking unless absolutely necessary. Use the comments box if you want someone else to check in.