This isn’t true. This is what the HA team tried to do here:
That was exactly the plan here. Acknowledge that users going supervised are going to do whatever they want and acknowledge that its impossible for the small supervisor team (just Pascal at the time) to support that. So keep the installer but basically say issues from supervised systems will be rejected unless reproduced on a supported installation method.
The community rejected this plan and demanded supervised be treated as a supported installation. So the HA laid out the boundaries of a supported supervised installation here and began adding checks every time issues come up due to users going outside the bounds of what is supported. Exactly as specified in that adr.
Whether this is better or not is clearly up for debate
But that is the situation.