How is 5.5e more confusing about compatibility with 5e than One D&D which makes no reference to 5e at all?
Because isn't 5e a "fan made" nomenclature? I don't think WOTC ever named it "5e". The playtest was DnD Next. The community calls it 5e, and 3PP companies refer to 5e.
There is nothing on WOTC's website about 5e either. DDB and WOTC mention "Dungeons and Dragons", that's it. Nothing about editions, or anything.
So if they continue to follow that pattern, OneDnd will just become "Dungeons and Dragons." And people will buy and play with the new books, and forget about the old books, like they do every edition. Because its just
easier. And new players won't care and will play the new edition. And old players, who still play "5e" will also pick up the new edition because its "official".
As someone (and a group of 50 somethings) who played 5e for several years, and stopped, and now play OSE, any desire for "backward compatibility" is nonexistent in our group. We don't care. Its super rare to actually use old material (classes, spells, etc.) in new editions, because we're using the "new edition." Everything else gets modified as needed for our homebrew settings anyway, even official stuff.
I personally, and my group, could care less what its ultimately called.