When you go to the channel, does it show you are still subbed even after you click on unsub? If not, what do you see that indicates you are still subbed to the channel? Blocking disables the channel from commenting on videos you own and does not hide their content from you.
That's odd. Mind sending a feedback report? All feedback reports are reviewed, but YouTube doesn't necessarily respond to every single one. We use the info to identify and fix widespread issues, as well as track requests and make improvements. Here's how: https://yt.be/help/feedback