The BSDs don’t have the critical mass to get this vendor support. For example, much of the intel WiFi work on OpenBSD is done by one person, Stephan Sperling, on a volunteer basis.
I only mention intel in the above examples because that’s what’s in the Thinkpad I had that didn’t have support yet. So I looked into the driver situation on Linux, FreeBSD and OpenBSD.
I don't have any numbers to back it up and I'm not sure if anyone even could know (does FreeBSD have any kind of hardware statistics program?) but I have a strong suspicion that the proportion of laptop users running anything even related to BSD other than Mac OS is fairly tiny. Beyond that, I suspect that many of those that do are using one of the same bunch of older Thinkpads that are popular with the kinds of people who work on operating systems. Devices that aren't used with those laptops probably don't get much attention.
Also 802.11ac in particular seems to mostly require firmware blobs, which are kryptonite to a lot of the kinds of people who would have to be developing these drivers. That's why you might have noticed that devices like the Librem 5 and PinePhone only have 802.11n.