(Here’s my favorite) The gaps between the beam and joists are fine and eventually the house will settle and the joists will bear on the beam. Putting in shims would be pointless because they’d get crushed and compressed when the house settles. (He really told me to wait until your floor sags and it’ll line up)

Is the contractor planning to come back and fix all your cracked drywall/plaster for free? Half the point of installing additional supports is to prevent any further sagging. Whoever did this needs to find a new profession.