I had a closer look and I'm afraid I was wrong. Mentioning a team account does not forward to the admins.
Unfortunately there's not a single, consistent rule to email forwarding for teams. Some events do get forwarded (things like permission changes), whereas others don't (e.g. mentions).
The exact rules might even change over time, but the underlying concept is that teams are not meant to be used as proxies to reach its members. You might notice that team accounts do not show up in the mentions dropdown.
Now we understand the value of being able to mention a particular group of people and we are currently looking into making groups mention-able.