I agree that it's in line with what we would expect from North Korea, but I don't think that having a motive is itself evidence of the crime.
They haven't even admitted to it, they've instead made a statement of "maybe" that I would expect from an elementary school child. To me, that smells like they want us to think it might have been them but don't want to look stupid (weak?) if someone else claims attribution for the hack after-the-fact.
