In my opinion, shadowban is a real. Of course platforms won’t publicly announce them, that’s why it’s called a “shadow” ban. You often see this when a video suddenly drops in views or a post loses reach, especially when the content is something you’ve never posted before. It can also happen if, before posting, your account logs in across multiple devices or IP within a short time, or if there are any sudden changes in general. That’s usually when the system starts questioning the channel or account and temporarily reduces distribution, until it decides the account is behaving normally again.