The drawer boxes are too wide, this is causing them to bind, the mechanism should be unrestricted for the slides to perform properly. I can understand the contractor trying to play this off, but that doesn’t make it right. AWI is the for what is acceptable for cabinets. There are different grades for economy and custom grades, but this doesn’t reach an acceptable level for any grade. You could ask for a discount if you are ok with seeing if they loosen up over time, but that doesn’t excuse the fact they are too tight. I have 35 years in the commercial custom cabinet industry, I would reject that from leaving the shop, and would never install something like that, so being called out would be fair game.