This would be dependent on the campaign manager if he would accept it. Maybe he is catching up with post count?
Maybe, usually depends on the manager and also on the quality post they write. But if it refers to the rules, then I think it's okay.
We have a post time limit per rank level, here's the formula based on what theymos say:
waittime = 360;
if(activity >= 15)
waittime = (int)(90 - activity);
if(activity >= 60)
waittime=(int)(34.7586 - (0.0793103 * activity));
if(activity >= 100)
waittime = max((int)(14-(activity/50)), 4);
Outside the context of a signature campaign, I think that burst posts can be determined by their quality, not how long the time interval is for each post. Any user who has activity points above 100 will be able to post between 4 second intervals, so of course if they post at 5 minute intervals or less than 10 minutes per post it's not against the rules and is allowed in my opinion. But if they are in the campaign then I think the manager will be stricter about the intervals.
I was going to mention this quote by theymos also, to my understanding the 360 seconds wait time only applies to newbie accounts. I remember being confused when I first joined the forum and tried posting simultaneously, I was warned I couldn’t make another post for a time, all this ended when I reached member rank. As for whether campaign managers should add this technicality that seems to be exploited according to OP to their campaign rules, I don’t know. I think campaign managers should have the independence to manage their campaign and participants as they deem fit.