Do as the body shop instructs. There are still solvents in the paint that are trying to escape while it's curing. If you seal it in, the topcoat may not cure to full strength/hardness. Eventhough it is catalyzed, and appears dry, paints take time (months sometimes) to gain full hardness. That is why a fresh paint job should be cut/wet sanded and polished out within the first couple days, and conversely, if left too long, it's no fun cutting/rubbing/polishing a cured polyurethane paint job. It will probably never match the luster of an uncut paintjob either.
You can play with overspray on the masking tape and bend it around all sorts of ways, and it won't crack. It took a looong time (many months?) before it eventually did crack on the masked portion of one of my projects (years?) yes long project
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I would go as far to say, even factory baked paints are still curing. That's why you can still smell them. I don't wax fresh paint until 1yr. But that's just me. You can buy new paint friendly polishing compound. Ask your local auto body supply store.