I flagged those because closed, low score unasnwered posts are deleted eventually anyway, it just so happens we're in a bit of extra pain in keeping them around. If I had I downvoted they would have been auto-deleted soon, but as is it would take them a year to disappear if they didn't have more than 2 comments, but as is they'll stay around forever. This is why it's fairly common for these to be deleted by mods as part of clean-up efforts. I've done it myself plenty.
Since they don't have answers and nothing helpful is in the comments (beyond discussion of why they're closed), they're good deletion candidates but they wouldn't normally require manual deletion. The problem is we want to be rid of the general Psychology tag, and digging through those brought up those closed posts.
Basically, when the post is providing 0 value to the community and won't ever (these have no answers and it's way past reasonable time to reopen them), deleting them isn't a big deal. It's a judgement call, but it all comes down to the mantra of Make the Internet a Better Place. If our site is slightly tidier by deleting some closed, 0 score questions that are providing no value, so be it. I've made this call on a few similar posts on UX as a mod.
And, as said, I could have basically "deleted" those posts by downvoting them. I just didn't think it was necessary to penalize the post owners.