Apple has the right to claim that using unsupported hardware is...well....unsupported. However, it sounds like they nerfed the driver which makes it a non standards complaint driver. This is a problem and Apple needs to be called out on it. At the very least, they could face sanctions or a trademark lawsuit from the display port standards group for using the logo with non compliant products. At the worst, a hefty fine from the EU.

Also, there's no point in "flooding" developers with support requests. Devs will rarely read what customers write anyways in large corporations like Apple. Better to push from the standards org or the govt regulator.