I do not know the legislative situation but I have seen KLM move a passenger from an exit row as they only spoke German, and either English or Dutch was required. But when picking the seat the app at least does not mention this only the ability to "hear, understand and act upon the instructions given by crew members", which can be argued is fundamentally the same thing. The crewmember in my case certainly spoke no German and a fellow passenger translated to enable a seat swap to happen.