I don't have a disposal ell to measure but as I recall they aren't much over 4 inches themselves. Did the manufacture say why a 4" drop was necessary? Your man put you in a tight job but unless you have backfall from the trap to the stubout, head pressure and the centrifugal thrust of the table should let you drain OK. If it bothers you why not cut the disposal ell back a tad and raise the trap to give you some fall? And don't sweat the attitude, we get it all the time. good luck, Tom

Correct me if I'm wrong, but someone said rough in at 18" for standard sized sink or 14" for a deep sink if a garbage disposal was going to be installed. Could I just rough in at 14" just in case I wanted to install deep sink in the future?

Could I just rough in at 14" just in case I wanted to install deep sink in the future?
Sure can! Your supplies and tailpice will just be a little longer. Good luck, Tom