The EU wants to not depend on US software.
The format is standardised. It might not be a standard you like, but it’s a standard that the US can’t “take away” from the EU. Microsoft, especially in cloud form, can remove access to Office tomorrow if they’re pressured to by the US government.
We might have a desire for better file formats. The EU doesn’t give a monkey about our crusade, it purely cares about not having US leverage hanging over them like a sword. And the underlying file formats, exactly because it’s a ISO standard (however poor it may be) is fine for this purpose.