I think a point is to be made that international treaties and alliances work on trust. They don't "oblige" a country in the sense that you may be obliged to do something.

Now the EU is not a military alliance per se and Article 42.7 (which was essentially sneaked in by the Lisbon Treaty) is a bit fuzzy so members will consider all aspects and offer some assistance, sure, but scramble their whole military because that's "all the means in their power", no unless they see that the threat to themselves is critical not least because the article also states that it "shall not prejudice the specific character of the security and defence policy of certain Member States". So basically some help will be sent but calibrated by all the usual political and self-interest considerations.