I don't know why can't they be more clear on this.
I made my son a gmail account six years ago. Somewhere along the way the google+ account appeared, which I wasn't too happy about. I did the deletion just as in your screenshot, and checked the "Yes I understand" box. The profile disappeared, but the gmail account was still fine.
(The profile came back, by the way. I suspect my son recreated it while at school.)