It would have to be? Says who?
For a whole bunch of reasons.
1) This EU military union is supposed to be about deterring Russia. If you give Putin's mates in Budapest and elsewhere the power of veto over its deployments then that doesn't really work.
2) Having 27 potential vetoes over EU military policy would render it essentially useless
3) France is not about to give Luxembourg or Malta a veto over where it moves its tanks
4) The EU is moving away from the national veto in general anyway
...and most importantly
5) Germany is not going to give up as big a prize as this