Personally I can't confirm this. I've recently replaced the battery on my 2014 Thinkpad, and on low brightness I get around 8h of battery. That is of course, while not doing a lot of compute (compiling).
I don't think this was much higher, back when I used Windows all those years ago, so I'm not sure what people are saying with low battery with Linux? I don't see how Windows could get me much more? And why would it?
If you have a Thinkpad, then the issues with the Framework (CPU sleep states, needing to turn of secure boot to hibernate properly, power management issues in Framework BIOS 3.06, etc) wouldn't necessarily apply to your laptop
