"Dean H." wrote in message
The reality is that if the window is farther out of the building than
before, there's really no way it's a tighter fit than the window that was
replaced. In other words, a tighter fit or better seal against the
building would result in the installer needing to trim something off the
sill, not add to it. The whole thing sounds fishy to me. The company
should be reported, IMHO.

Not necessarily.

Many years ago I had a sideline business selling and installing replacement
windows. These were pre-made units that slipped in where the old sashes
were. There is a stop on the outside for the old sash. We just ran a bead
of caulk and put the new unit in place against it, drove a few screws, put
the trim back and it was done. If, for some reason, the sash was thicker
than normal, there would be a gap at the sill. There was, normally, no
reason to touch the sill. If there was a gap, we carried some prepainted
wood trim to put in place.

At the time, we were paying $35 for a window unit and charging $55
installed. That was $20 every half hour! Big bucks in the 1960's.