Battery life is an area that may be difficult for smaller phone makers to compete on. I think Apple especially puts a ton of engineering effort and coordination into making iOS and their apps work efficiently with their hardware, reducing complexity, runtime cycles, and power consumption as much as possible, on top of already highly-efficient ARM hardware.
Over years of doing that (kaizen), the result is optimized hardware/software fusion with industry-leading battery life. But it seems like it takes a non-trivial amount of additional engineering time and effort to accomplish this, that will be difficult to match by smaller mobile tech startups.
I hope the open source community around Librem and Pine will be able to replicate that effort, but I'm not sure this kind of consistent incremental upgrade work is attractive enough to volunteer FOSS developers. And being maximally effective at it most certainly requires the parent company to coordinate the effort across hardware, software, internal teams, and external volunteers.
Sadly I cannot confirm this for my 6+ different laptops I owned. And I tried all the crazy settings, grub, tlp, .. and even compiling the kernel myself.
It is hard to beat loads of dedicated engineers, who are paid regular and well and have access to all the proprietary device information and even manufacturing.
edit: maybe there was one time, when a linux stock install performed maybe equally than a stock windows install. But that was only because of the windows bloat, which linux does not ship. But I can easily remove most of the bloat, but I cannot just write a better gpu driver. But if windows continues its bloat path, it will be soon inferior despite way better drivers.