I notice a similar behaviour. I don’t have a Google account and don’t keep cookies, so the only way for them to track me is my IP.
My IP seems to be permanently associated with my YouTube habits. They’re even being sneaky about it, as in they’ll give you a default homepage and generic recommendations first, but watching any video similar to the previous viewing habits will bring back not just videos related to that one, but the entire history they’ve collected over the years (some of the topics I watch are completely separate and would never intersect normally, so the only way for them to both come up in suggestions is from previous viewing history).
I didn’t create an account, didn’t agree to any privacy policies, and am blocking any and all cookies just like they advise in their own privacy policy and yet I am still being tracked.
An anecdote: I stayed with relatives for a few days one time, and my two-year-old niece really liked one particular music video on YouTube, so it got played on their TV box 3-4 times during my visit. Not on my laptop, but I used said laptop on their wifi (not logged into Google products, as I never am). When I got home, YouTube highly recommended that video to me after I watched an unrelated video, when there was no other reason to recommend it (I didn't know the artist, almost never watch music videos, and it wasn't anything all that popular).