I would say that installing Linux is like being able to tune your guitar or a chef being able to sharpen their knives, but it's an order of magnitude easier than either of those things.
Agree with sibling that maintaining preinstalled Linux is a good sign that all the guts and peripherals are compatible, although that might be a perverse incentive to use a bleeding edge kernel/distro to accommodate flashy hardware. If anything, they should install a boring LTS/Debian Stable, completely stock other than a custom wallpaper.
For personal laptops/desktop I don't care if it's preinstalled for me or not since the very first boot is going straight into my usb installer since it's extremely unlikely that they checked all the boxes I will check (especially getting my LUKS passphrase correct!!). But for my wife or parent's laptop that's exactly what I want. If dad runs linux I can help him out a ton more, even SSHing into his machine to set things up or install updates, etc, but I'd prefer he be able to turn the thing on and connect it to his wifi and start using it without me having to be there.
I think this is doubly true when you consider the elevated support task they have by the nature of how upgradable/repairable the laptop is. The number of issues I’ve seen from people (and I’m just an owner who lurks a bit in some of the communities) who didn’t know how to properly insert RAM or have had other more basic problems (which is separate from the more widespread issue of installing the wifi cards, where the antenna cables were legit the most difficult I’ve ever dealt with and I have years of experience — Framework sent me a replacement cable and card and that was great), makes me sympathetic to them trying to grow their support teams at an even pace and not inviting a bunch of support queries that can tie-up even the more established Linux hardware vendors.
So yes, I agree, better Linux support would be great. The good news is that it’s already becoming an enthusiast computer so Linux support, especially on newer kernels, is already better than on many other enthusiast laptops (the suspend issues and some recent kernel regressions for wifi are obviously issues but they aren’t isolated to just the Framework), so hopefully that will help. But a hardware startup can only focus on so many things and if being explicitly Linux-first isn’t one of those things (and due to market size, I think that probably makes sense when you have mainstream aspirations), it probably isn’t a good idea to over-promise in that respect — especially when the DIY options and unofficial support is really strong/encouraged.