I think that pre-installed Linux also means that company is going to provide some customer support, be it BIOS fixes or maybe addressing a driver issue after an OS update.
Without such support it was common to simply get “an unsupported OS” reply, which will necessarily limit how popular product is with non-tech people.
Yep. I've had my X1 Carbon for eighteen months and keep receiving firmware updates via lvfs. Every piece of hardware, fingerprint reader included, works flawlessly out of the box with Fedora.
Using several x1 carbons and also a T14s under Arch Linux and no problems at all. It's a great machine. Bios updates can be had also, just like you said.
Without such support it was common to simply get “an unsupported OS” reply, which will necessarily limit how popular product is with non-tech people.