That is a matter of perspective and to some extent relativity…
The r8000 has bcm4366 wireless, which is an uncommon choice for a router, as it uses a fullmac chipsets compared to the more commonly found softmac based chipsets.
Broadcom does (did, they formally stopped a few months ago) support fullmac chipsets via the mainline supported brcmfmac driver, including AP mode. While brcmsmac exists for softmac based chipsets, that driver only supports an old client-centric chipset (bcm4331) and doesn't support AP mode at all, the bread-and-butter softmac router (and highend notebook-) chipset bcm4360 is not supported by brcmsmac and remains totally unsupported (apart from b43, at 54 MBit/s max).
That is the situation described in the wiki - and it's 'correct', in the sense that we have a mainline driver for this hardware (compared to …crickets… for the more common softmac based routers). But as you noted already, the situation is not all roses for this driver either, Broadcom lost interest in actually maintaining it years ago (probably their main intention was to kill off b43 development), and as these chipsets are more commonly found in client devices (phones, RPi and other devboards) and relies much more heavily on the firmware to handle the connection in hardware, it also lacks features (AP-STA mode is not available, so no way to act as repeater, WDS/ 4addr or mesh node, limited interface combinations, etc.) compared to better drivers. And after Broadcom sold their wireless business (particularly the fullmac designs) twice, once to Cypress, another time to Synaptics (and still retaining some parts to themselves), they neglected development over the last half decade (before formally orphaning driver support a few months ago). This also left the driver in an odd situation, with some parts (firmwares) having to be provided (at least signed off) by Cypress, some parts remaining under Broadcom's umbrella, so the situation is a mess - and has only gotten worse.
Keep in mind, this router is a decade old by now, released at a point when 802.11ac devices were still spanking new on the market - and this device was one of the first that actually got mainline supported and supported by OpenWrt (back then, in the 2013-2016 time frame, I actually strongly considered buying one myself), but it remains an exotic device (SOC/ wireless chipset) in an OpenWrt context among developers and users, which is never good for long term maintenance…
So understand the note on its device page relative to the even worse situation for Broadcom softmac chipsets (bcm4360), which isn't supported at all (insert b43 disclaimer here, but you aren't buying an 802.11ac device to be limited to 54 MBit/s in 2024). It certainly not a recommended device (and especially these days there are plenty much better, much better (OpenWrt-)supported and much faster (802.11ax or just 802.11ac/wave2) alternatives. It's certainly not a device to buy in 2024, even less with OpenWrt in mind - it's an exotic option for OpenWrt and Broadcom doesn't care about it anymore (and probably never really did). Given the above, the quality of OpenWrt's support might be lacking, it has few users and the remaining ones may very well be the first to find bugs - and end up having to fix them (or it remains broken) - it is not expected that the situation for this hardware will change in the future (on the contrary). If you are looking for well supported alternatives, your options are between Mediatek and Qualcomm, not NXP (ex-Marvell), not Realtek, not MaxLinear (ex-lantiq), not OnSemi (ex-Quantenna) and certainly not Broadcom.
Disclaimer: Only speaking for myself, not the project nor its developers. I never owned this device myself, just strongly considered buying it a decade ago (and therefore kept closer attention to it ever since). While the wiki note itself is correct, actual device owners augmenting it with their actual experiences (summarizing the current situation) would be appreciated.
