Regarding the height difference, the question for me is: how high was the screed supposed to be according to the plan, and how high is it actually? That’s where the significantly greater risk lies: is there still enough coverage of the underfloor heating ensured? Or will hopping once in the bathroom cause the screed and tiles to crack? On the topic itself: I think it’s better to be too high than too low. From a certain age, many people use toilet seat risers, which you already have as standard. Basically built barrier-free with foresight. I don’t find it so serious, for the few minutes you effectively spend on it daily.