I think a lot of the "why does it take so long" sentiment comes from the fact that a lot of the back and forth seems to be just a complete waste of time. Some (most? all?) dealers seem like they would rather spend time proving something "normal" by finding another truck that does it, etc than just actually troubleshooting the issue. Then if they cant do that, they'll go into "by design" mode.
We've now proven that a tech could have done more than just say "its shutting off early for some reason". They can actually connect to the darn seat module and know EXACTLY WHY it's shutting down early. And once they know that, they might actually be able to fix it. And even if they couldn't fix it at that point, at least the explanation could be more of an explanation than just a generic "yeah its shutting down early but thats what its supposed to do if it senses something wrong".
But alas, its easier for them to say "sorry its normal". I understand warranty labor rate is less than out of warranty labor rate, but again that goes right back to "it takes too long because ", and in this case they would be putting profit before the customer.
Think of it this way...if this truck was not under warranty and taken in because of the seat heaters shutting down early, would the problem have been fixed? I honestly think it would....at the cost of a whole lot of labor, but yes I think it would have eventually been fixed. Because they would be getting paid 100% labor rate instead of some lower amount, they could throw a couple hours of troubleshooting at it, potentially find the exact issue and then throw more labor at it to fix it.
Ive owned: Chevy, Dodge, Honda, Acura, Infiniti, Nissan and Lexus. The Honda, Acura, Infiniti and Nissan's have all had "issues" (not major) under warranty. At no point did one of those dealers try to excuse it away. I walked in, explained the issue, showed it to them and they fixed it.
My Chevy, Dodge and now RAM? Same runaround - first it was normal, then it was "oh its this", which didnt fix it. Then it was "oh sorry its this", which also didnt fix it. Then it was "sorry we cant fix it so it must be normal".