I need my crank turned if possible as #5 main bearing journal looks bad. It many not have enough meet left and I need an exchange. I want it balanced if I'm going to have it turned. (This is a 2.8 L V6 from a 1980 Citation.)

My question is:
Shop sez; they need :" the pistons to balance it". This shop has best rep in Valley so I don't think he's lying--may not want to do the job-?
I've heard: They attach weights to simulate piston/ring/rod/wrist pin, etc, weight and don't Need the original parts.
How can a rebuilt, balanced crank then be balanced If the shops need the pistons?