IMO there is no obvious reasons for Dale to remove the decals at the condo, either in the driveway or in the garage, Michelle has been at the condo dropping the kids off presumably many times before (not 100% sure here), and an H3 is something people don't just notice but usually stare at, and decals are there for the simple reason they attract attention. Dale could not count at all that the hammer would not be spotted arriving by a neighbor already familiar with such a vehicle at such a location, nor could it count on the same neighbor not noticing the obvious absence of the decals at departure, a piece of evidence he might have no way to explain when confronted by the police.
IMO The remover of the decals here are consistent with everything else we know about the perp: a methodical person who makes reasonable cost-benefit analysis and acts accordingly. Here, at least in one theory, he needs to drive as far away as possible from the point of abduction but with a vehicle that is very noticeable and with large decals, one instinct might very well dictate the immediate removal of the decals, but that would only decrease to a degree the risk of a more precise identification of the vehicle as belonging to MP, but then again so would the license plates themselves, conversely he could simply step out from the relative safety of the interior of the H3 provided by tinted glasses and take a chance on being identified, again the cost-benefit analysis here are clear to the perp, he will continue on driving to his destination where the decals will be among everything else he can safely dispose of.