Don't expect something more than a canned response. It's not that the creator support doesn't want to answer more, but if they do, they risk the answer being spread to the public and getting even more PR disasters.
It doesn't need something to trigger it at all. After the latest fiascos with big YouTubers they just enforced stricter policies. But, if the so called algorithm and the AI can't determine a video as advertiser friendly, it will flag it as NOT advertiser friendly, to be on the safe side. That means even a perfectly suitable for advertisers video can still be flagged as not suitable.
The algorithm and the AI don't think. They are software programs that scan the videos and mark them as advertiser friendly or not.depending on criterias that YouTube won't reveal, because they will be abused by the creators.
For the record, I was first here to report the Yellow demonetization icon --> yttalk.com/threads/youtubes-new-high-low-for-monetizing-videos.265757/ and I was one of the earliest members that was hit with this problem. Since then, I had more than one thousand videos marked as "not suitable for advertisers", and 99.93% of them were restored after I appealed. So far I had issue with only one video of bikini girls dancing and teasing (no full nudity but still sexy dances) that was confirmed as not suitable. The situation bothers me a lot, since it reduced my productivity, but we are here because of the big YouTubers that went further and further to shock and please their subscribers and we got Adpocalypse 1, Adpocalypse 2 and now nearly Adpocalypse 3.