I read some campaign manager sentiment about this issue. Forcing their participants post above the minimum post requirements they set by themselves. If they want a higher post quota participants, They should increase the minimum post requirements or make the campaign rate per post without any consequences for posting low but quality post.
There's no right post quota per week, each campaign is unique and the manager decide what the post quota is, if you're not comfortable with the rules then don't participate in the campaign. As a signature participate, you're an employee of the campaign manager and his rules are his for you to follow or you get removed from the campaign. The minimum quota rules are there to give the campaign some amount of weekly works but you shouldn't be making just the minimum, if you're doing so then you're indirectly telling the manager that you're just there to make money and such users aren't useful to the forum because their posts aren't usually quality but just there to make up the weekly quota.
There are so many campaigns on the forum therefore you're free to join those that suits your posting styles and habit. I did a thread on that few years ago titled; [Guide] Factors to consider before joining paid signature campaigns but many people just join any campaign available and then begin adjusting their posting habits or style to fit the campaign and this usually drops their quality. For example, some campaign requires you to be active for some specific amount of days (judging from their maximum daily post count) so if you're not very active on the forum, you shouldn't be joining such campaign. Every campaign manager wants the best for the projects that they're managing as such users that aren't promoting the project effectively to their tastes can be removed at any moment.