I’ve been told by my credit unions that each uniquely-named account is insured, by National Credit Union Share Insurance Fund in this case, up to the $250K limit. ie: you, your spouse, and another one owned jointly by both of you, for a total of $750K.
This is a good explanation of What is an insured account: FDIC Insured Account Definition, Requirements, Pros/Cons (investopedia.com)