If I was releasing a laptop with Linux support as a key selling point, and the battery life was bad on Ubuntu 24.04 but good on the pre-release 26.04, then I'd advertise the good figures and write "tested on Ubuntu 26.04 beta, requires Linux 7.0 or later" in the footnotes.

I definitely /wouldn't/ rely on just Windows figures for a machine that's otherwise advertised as "Linux first". If the battery life was the same on both, I'd prominently mention that.

I'm a long-time Linux user who might actually be in the market for a just-works upgradeable laptop[1] that comes with Ubuntu.

I already know that combinations of hardware and software can be stretched and tweaked to do really interesting things in really excellent ways. I don't need them to tell me that computer systems are flexible. That's just noise.

And I don't want them to tell me how their (unreleased) hardware might work in the future with some unreleased/beta software. That tends to be interpreted as speculation, or as lies and deceit.

I'd prefer to see benchmarks of how it works if it shipped today.

If those benchmarks are unsavory (as they may presently be) and thus omitted, then that's not ideal but it's okay.

I definitely don't want to feel as if I'm being lied to, in place of an omission.

[1]: I just want a 15" version. I'm not a fan of little screens. My eyes aren't getting any better.