The main reason I see for making gender of NPCs easiy to identify is to inform the players of the structure of that race's society. It let's them see what roles members of each sex play and from that they can extrapolate more information about those societies.
I don't know how other GMs handle descriptions, but when describing NPCs, I don't talk like this:
"You see an elf. It has small/medium/big boobs."
I talk like this:
"You see a female elf/elvish woman".
I don't know how other GMs handle descriptions, but when describing NPCs, I don't talk like this:
"You see an elf. It has small/medium/big boobs."
I talk like this:
"You see a female elf/elvish woman".
If you drew a picture of the fight though, the elf would probably have small/medium boobs (big boobs on an elf are just wrong.
That is not what large breasts look like.