I bought a house with pretreated hardwood floors. I used something to try to clean them and it took the shine out.
I called someone I have used in the past to get an estimate on refinishing them but my husband says they can not refinish pretreated floors.
The contractor said he can do the lightest (level 1) sanding and put a new finish on- which will not buff out any deep scratches (which we only have 1 or 2) but will get the floor looking good. Is that true?

Depends on the "treatment". IF the floors have a urethane finish on them now and have NOT been waxed, oiled or polluted with products like Endust or silicons, then they can be lightly abraded, cleaned thoroughly and recoated with a urethane finish. This will NOT fix or repair dents, discoloration or deep scratches. It usually makes the floors look much better and provides an additional layer of finish to protect the wood. If the floors have been waxed, they can either be cleaned and rewaxed or completely refinished by sanding, staining and finishing.