[...] No one when first connecting to an sshd goes to google the key to see if its valid, they type "yes" and carry on.
Not really true. Some people are more cautious than that.
Anyway, lots has been said in this thread, but I suppose nobody has mentioned that running sshd on port > 1024 is pretty common nowadays.
I know that my hosting provider runs sshd on port 5757.
It is probably to buy some time in case there is a serious sshd vulnerability. The port scanners would usually scan the port 22 and my hosting provider might have enough time to patch their sshd.