Yours and other comment did reveal my analysis was flawed, thanks for that.
Re: the first two points, I really don't think so. I have a Nexus 5x that would kill the battery in around an hour if video chatting (to your point, it did get very very hot). There is also a recently revealed 'bug' in the NXP SoC being used by Librem themselves, who claimed it was killing the battery in an hour. I figure anything under 2 hours is fair game to be 'measured in minutes.'
How old is the battery in the nexus 5? It's a 5 year old phone at this point. Daily charging could have put it through 1000 or more charge cycles at this point.
Re: the first two points, I really don't think so. I have a Nexus 5x that would kill the battery in around an hour if video chatting (to your point, it did get very very hot). There is also a recently revealed 'bug' in the NXP SoC being used by Librem themselves, who claimed it was killing the battery in an hour. I figure anything under 2 hours is fair game to be 'measured in minutes.'