I would certainly ask the dealer to open up the tail lights during PDI. If it has been on the lot for any length of time, there is probably already water inside.
Otherwise, if you want to keep those lights, I would at minimum silicone seal the gaskets to the backwall, but don't silicone the tail light lens itself to the gaskets.
Silicone works well in this application as it is semi-removeable.
I keep a product called JWB Anti-Bond in my toolbox, which essentially debonds sealants. It can be hard to find though. It works better on polyurethane sealants than silicone, but it seems to semi-work on silicone.
Antibond 2015
There are other products especially formulated for removing silicone, but I have not tried them yet.
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