On a map with really bad cading spots, or even escape maps, are people allowed to go into spec at the end of the round, then wait until zombies spawn which then they join a team as a zombie?

On bad cading maps, they take away a tag from zombies by automatically being a zombie, and are most likely to live because of the crappy cade spots.
On escape maps, zombies usually live anyway and zombies are the ones with the best scores at the end.

Just seems like an exploit in the ranking system. And I am sure those that care about rank won't appreciate those that do this.

-edit-
Just thought of something else too.
Since the person is in spectate, they can now find out where everyone is hiding then spawn as a zombie and go right for anyone hiding in a vending machine, or behind objects zombies might not look behind etc.