I don't think it is changing the goalpost. The law prevents more than half of Germany's inhabitants from installing ACs, because they are renters. Also landlords cannot just install AC just fine. If you just own an appartement, you need the consenst of all other owners in the building. This is also a law. Therefore, practically no landlord will agree to the request to install outside AC, unfortunately.

It sounds like a case for having more laws / regulation. Rental properties should have a maximum temperature, else they're not liveable (same as if they were damp or infested).