Re: There is an official update available from Apple
It's not quite that bad: hardware tends to receive OS updates for 5-6 years, which in terms of a business device, is reasonable and better than many Windows PCs, which by that time may still be receiving OS updates from Microsoft but the manufacturer has long since stopped caring.
That said, the policy is somewhat arbitrary and annoying. I have a perfectly good 2010 MacBook Pro with a refurbished battery that, for Apple's own reasons, can't go beyond Lion. So, it's just sitting around waiting to go on ebay, because there is at least still a market for it.
I'm still on Catalina with my 2020 Intel MBP and my reserve 2016 MBP (you have to have a reserve not least because of battery issues with Macs and this one too has a new battry) because I'm waiting for Apple to fix all the problems with their new architecture and merging with IOS. And I also need to have the same basis for hot-swapping, in case of hardware failure.
That the patch for the graphics driver has not been released for the older versions is disgraceful, though I assume Apple will get round to it when it suits. IANAL but I don't think the argument that there is a new version of the OS would really wash here because the new OS comes with new T&Cs.