OEM paint loss in rain rails- is this normal?

no poseur said

I don't see how the por 15 could crack there, unless your cars rusted in two at the floorboards and rocker panels it's not gonna flex.

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That is the reasoning I used, and the rust encapsulator is tough as hell.
I figured if the seam sealer tends to come away from the body metal anyway, how could it be that the POR15 that flows down into the seam be a bad thing.