Even if it's a small scale, what really matter is the "repetition of botting behavior". Repetitive IP alone doesn't mean much. People can binge watch Youtube using one same IP, and their views are valid.
But, when we want to watch mostly only our videos, repetitively, then there is a problem. Inevitably, we will do botting behavior. Too many repetition of (combination) : same IP, same device, same footprint, etc in short of time.
Usually at first it goes well, until Youtube anti-bot detection is triggered or catching up, even after we try to mimic human behavior manually, using different proxies, etc.
The main reasons usually because we are not patient enough and then do manual botting, instead of natural browsing.
Let's talk about numbers. How many do you expect you think you can get from your 1 phone and 1 proxy per day? Or rather, test it out yourself how many is "safe" before the views started getting dropped