There is no such thing like a destructible group. This function does not leak, it just iterates through all destructibles in that area and since the playable map area and obviously the destructibles themselfs are preplaced this function does not create any new content which might leak memory.
Even if you create more of them, it is still just an iteration.
Only those variables leak which create something new. Unit-Groups are real objects which need additional space for management issues, if you pick destructibles though you only pick one destructible after the other from present destructibles.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory