It has! I've been using Ubuntu on a thinkpad x1 carbon (2017) for almost a year. Battery life is between 6-8 hours everyday use including work. Probably see between 8-10 if I'm not doing any programming

No. Linux can’t match Mac OS on battery life.

Mine has, older Linux on older Lenovo was not good but also that battery was aging.

New (<1yr) Asus gives me about four hours of 30+ tabs across two indipendent chrome profiles, my heavy editor, multiple active ssh sessions, other nonsense, keyboard lights (on low) and screen at 60% bright.

I think it's very good.

I don't have any firsthand information, but I've heard power management has gotten a lot better for both Linux and Windows and the laptops advertise comparable hours (with reviews not calling them out on it). There are a few name-brand laptops that offer explicit support for Linux distros. Those might gave you a better idea of what to expect.