I've done this on many drawings when I worked with ISO but now I'm an ASME guy and never seen it this way.
Still doing it because it's easier on very simple parts.
My old books referencing MSZ EN/MSZ ISO used these. Back then I did not have up-to-date info. It's still a valid method I think. I know putting Datum A on the shaft is not that hard, but still. What's the reason to reject it?