Interesting ....
First, hasn’t Disney made two movies using the name Navy Seals. One with Charlie Shean and one aimed at kids. So they must already have some rights to the name.
Second, I’ve worked with the US Armed Forces before and getting licenses to use images (i.e. the Thunderbirds) is very easy and very inexpensive. Disney would be better off getting a license to use the name rather than trying to trademark it themselves.
Except by trademarking it they have exclusive rights to it.