A "Ban" would be a action taken against a member for an indiscretion.
The message is simply a "housekeeping" task - the bogus accounts will be deleted. Can't "ban" a user if they have done nothing against the site rules, or if they don't exist.
We were receiving feedback from members that joined up in the first two weeks of the site becoming live. Then they logged in two weeks ago. We have progressed since the early days. Comments like "This site was dead when I joined, but now it is thriving". So we thought it would be a good idea to let people know that we are established, and to remove the "fake" accounts - If they exist.
So far the net result has been the introduction posts of a couple of formation members and some confusion over our intent.
I hope I have cleared this up.