No its his post, it mainly depends which side of the argument he wants to follow. If the campaign is indeed open for new participants only for short periods of time, e.g. when someone leaves. I would put them in CFNP. If the campaign is only full form time to time or only full for certain member groups, I would say they should stay in active.
To me it sounds like the 1st scenario.
At the moment, that would be correct.
But since the post isn't updated in real-time and a campaign jumping between Active and CFNP would be a bit odd, you should also consider:
I would like to be considered for this campaign
-snip
Enrolled on probation -snip
Last user was enrolled 2 days ago, post check is today and most probably spots will open up.
In my opinion the period where all spots are filled is usually shorter than the period where they aren't,
but as you said, it's on Mitchell to decide how he wants to list a campaign like that.
EDIT:
Besides that, crypto-games.net does no longer enroll any junior members. Numbers for misc are
S: 3 slots, F: 6 slots, M: 4 slots. J: 8 slots.Also, I don't know if it belongs into the misc sections, but they are allowed to use their referral link in the signature while being enrolled.