Yes, the difference is the latter means "it is no longer maintained", and the former is "they claim to be maintaining it but everyone knows it's not really being maintained".

in theory "maintenance mode" should mean that they still deal with security issues and "no longer maintained" that they don't even do that anymore...

unless a security issue is reported it does feel very much the same...

"Critical security fixes may be evaluated on a case-by-case basis" didn't exactly give much confidence that they'd even be doing that.

Given the context is a for-profit company who is moving away from FOSS, I'm not sure the distinction matters so much, everyone understands what the first one means already.