Normally dual use means it has a possible use as a weapon. Compute power is restricted from export to enemy nations and is considered dual use. There was once a moment when a Mac had enough computing power that it was prohibited from export during a few months until the new limit was established, which was cleverly used as an ad: https://youtu.be/l2ThMmgQdpE?si=xgLsybj86ErWnGvR

But in this specific case it’s utter clickbait.

Dual use: https://en.wiktionary.org/wiki/dual-use

Dual use as in desktops + servers.

It means you're paying for functionality you're unlikely to use.

Dual-use means you can use it as a nice place to put e.g. beer cans on it when closed or watch cat videos when open.

Maybe it means they'll finally ship Apple Silicon servers that have a comparable amount of RAM to their Intel rackmount models.