It would seem it takes in account a bit more than "visual similarity", otherwise I can't find a good reason for "@" and "U+1F582 (BACK OF ENVELOPE)" being that close.

Also, for years (decades?!) I wanted something similar in Word, for when I knew how to describe the symbol in words, but had a hard time manually searching for in the unwieldly UI. I can't believe that "insert symbol" window still doesn't have any kind of search capability.