Deeming this an exploit and giving admins power to ban over it is problematic, to say the least for the following reason.

An admin cannot distinguish between someone who uses zspawn and:
A. Had intentionally spotted a human beforehand
B. Who had happened by chance to see the location of a human before spawning
C. Who did not know the location of a human before spawning but happened to find them afterwards as a zombie.

Essentially, this would allow an admin to ban any one who spawned and then tagged or found a human.