I'm pretty positive Youtube does this sort of testing on certain selections of accounts. There are people who just get lucky and never have issues, but also others who absolutely get targeted and destroyed by their tactics. It applies to all sorts of things, shadowbans, auto-moderation of content, etc. There is no defined rule set.
I definitely see this with Youtube comments where I will constantly be getting shadowbanned for no reason, posting completely benign, normal conversation while others will get away with way worse or even the exact same thing I was trying to post. I've been completely shadowbanned from several channels despite being on good terms with the channel owner. And everyone knows how totally unfair they are with enforcing arbitrary policies concerning content and channel bans.
I've spoken to Youtubers about this and there have been theories that hardware or cache/cookies or other user-end things could be cause, but I'm pretty positive it is exclusively on Youtube's end.