One my first ACT in October I went in with No Prep and I had could not function at at all because of stomach virus ( I wasn’t just going to not show up to the ACT) I scored a 17. Then I spent my entire winter break break studying an signed up for an ACT course. When I took my ACT I was confident and I am sure that I scored at least 31, because I had my friend time me taking previous act test every week and my scores went up constantly reaching 32 at its highest. Will the ACT find it suspicious and cancel my test if I got from 17 to around a 30 or is there a chance they will simply just ignore it.
I think that you should be prepared to explain the jump in your score. However, your post makes it very clear that you already are prepared to do so.
Is I likely they will leave my score if I have a decent explanation.