Most learn to exceed it by a minimum of 1 or 2,  otherwise they risk not getting paid should a post get deleted before the final count is in. I believe a decent amount of these users do have other accounts they are either still trying to grow, or are registered in a different campaign. So they move to that account to complete the posting; sometimes they alternate between and talk to themselves.

You are right that any campaign could increase the post count they are looking for, but this also comes with the risk of passing over quality posters with lower frequency of posts. It's silly that a post buried in the page 26 carries the same weight as say an OP that gets read viewed 100+ times. It's just the advertising metrics you can work with here on the forum.

So I still just fall back on the issue with multiple accounts in a single campaign being that the participant is already being paid to post for that campaign to a minimum. This minimum though shouldn't be viewed as "piece work" where you can come along with a second account to get paid for recreating it. Minimums are generally in place because people have varying talents and abilities, and when you employ someone you have a set minimum that makes them worth employing.

In this hypothetical are the alt accounts supposed to identify that they are an alt? Not sure if I missed that. If not this opens up further cheating potential  against the  advertiser. The multiple accounts could reasonably recreate say 60% of their posts in a similar fashion, or just "conversationally" post their own back and forth.

My entire stance is from the perspective of someone paying to advertise on the forum. I don't think that this campaign standard has anything to do with spam suppression. I see it solely as people not being able to grab a second paycheck for 1 job.