I think the thing you need to communicate most clearly is the expected time to review requests.
I've worked in webdev and 100% understand the need to keep spammers from abusing your system and the issues it can cause for your other operations if you don't properly vet folks using it. The actual process of approval was never an issue, the major problem is that you don't communicate how long this will take. For example, I am used to dealing with services with response times within a day or maybe a few at the outside. That being the case the notice you've added would very much have not solved the issue for me, which was rooted in being unaware that your approval process would take (what I consider to be) an extremely long time.
At the end of the day, though, even if you were to give a pessimistic estimate it can be incorporated into scheduling and project management. Having something is better than nothing, because regardless of whether or not you can speed up your timetables for approval, you'll always have the issue of creator being forced to guess how much time those internal processes take.
Also, this is a side issue but worth pointing out: I actually did try to contact your support team and as far as I can tell doing so did not expedite my request. Do you have any kind of triage/priority system? The impression I got was that you handled support requests chronologically, so I'm a bit unclear how contacting support helps here.