It could be that they just don't want to deal and test with older versions. By only specifying a certain number of supported displays they essentially guarantee it works for those, that doesn't mean however it can't work on others, you just don't get the assurance of it.

I have never really brought it when they say that they are disabling some feature because they can't support it, as if there's an avalanche of phonecalls that is swamping their tech support resources. By that logic, why don't they just disable support for any third party monitors? Actually, better not give them ideas...

They haven't disabled it, they just don't officially support it. It works fine, you just can't get help from them if it doesn't.