1999 Pontiac Grand Am Engine Replacement

I currently need to replace the motor in my 99 Grand Am. The mechanic I took the car to quoted me for a "10 hour job, " presumably the standard time listed in Chilton's, etc. I purchased motor off the internet and when it arrived at the mechanic he said the water pump was leaking. Okay, no problem, but now he says it's a "6 hour job" with the motor in the car, but since the motor isn't in the car it's only a "5 hour job;" in addition to the 10 hours to swap the motor.

My question is: Isn't the time required to swap out parts from my old motor to the "new" motor, such as alternator, water pump, etc already calculated into the 10 hours to swap the motor? I have no problem paying the lised labor time (even if the mechanic will probably complete the job in half the time), but it seems like this mechanic is trying to charge me an additional 5 hours labor for a job included in the 10 hour motor swap quote.