I agree, but I am sure he has his reasons. Just because you have the knowledge doesn't mean you have the time. (being a student I lack both most of the time!)

Anyways, do you still have the instructions? See if there is some sort of mark on the heater saying which side is supposed to go where, and if maybe the mechanic put it in backwards. Next, see if you can re-arrange the hose that is already in there to eliminate the loop, because I do agree that it would seem to cause a problem (especially since the instructions say not to)
If that doesn't solve it, I would head back and tell them to install it right, or head to DIY.

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1971 220D/4-speed ~250K mi. Family owned (dads side) through three generations since <5K miles.
1992 Chrysler LeBaron, 3.0V6 125K. Family owned (moms side) through three generations since new.
1977 Chevy Camaro Continual hotrod project
1970 Cadillac Sedan DeVille 472ci and nearly 19' long
1974 Fiat Spider Still needs work