The seal does matter for notebooks. I've repaired Lenovo and Dell books because they had inexplicable junk inside. Although a laptop can't usually survive total submersion or liquid poured on top, there are situations where keeping the bottom and sides sealed is helpful. This can also be achieved with rubber and some other techniques, but either it's thicker (another tradeoff that buyers don't want to make, for whatever reason) requires more complex manufacturing (which affects quality in other ways, or price--more tradeoffs.)
There are definitely thermal issues with MBPs in regards to performance and comfort, but no common ones that affect the glue. I welcome correction here, but if heat improved repairability so readily, we'd see that technique recommended and applied more often.
Edit: I saw your comment was flagged dead. I didn't do that. I vouched for it to restore it.
It seems like you stan for Apple no matter what, so it's not surprising that you defend this sort of thing, but this is straight up shitty build quality, and Apple really has no excuse. As the premier brand, they need to be doing better by their customers.