Yea, but EU can of course have a common standard and not make it mandatory. It’s not more strange than US making federal standard vs different standards in each state.

Yes I agree, and this would be the ideal and most efficient outcome, and it should be repeated: an EU-wide common standard, which can then be optionally adopted by businesses in each member state alongside not forbidding existing invoicing methods.

In this scenario we can anticipate that business practices will shift to the common standard over time, and that would include the accounting software used by new businesses: resulting in a phased conversion with minimal disruptions to running a business.