Well I have been noticing these things for so long. I can only tell you my observations. First of all I never had notifications ON for any channel ever. So I only watch videos from my subbed channels when I see them in feed.
So last month I unsubscribed a PUBG gaming channel, and for few days the channel completely disappeared from my feed and recommended video, while I was able to see other PUBG gaming channels.
Somehow after few days I saw that channel in recommended section of another video. Thing is it only showed me that channel because the topic/keywords of that video was very similar to the video I am watching right now. ]
So in a sense youtube treated that channel just like any other channel that I haven't subscribed to and It only shows its videos if the video is similar to what I am watching and is successful enough to be recommended.