How is it nonsense?
The EU law is that the reject all should be exactly as easy as the accept all button. 1 extra click, however minor of an inconvenience it is, is extra effort. And therefore strictly speaking in violation of the law.
Nothing will ever happen but it’s valid criticism.
They cannot back feed when there is no grid power, yes. But they cannot differ between power used inside the house or outside the house. They can and will definitely push power back out to the grid as long as they detect grid power from other sources.