Before starting, yes adaptive history is turned on, and with enough characters this behavior will engage, but the threshold is still too long. In the below example, I have cleared all history and saved data. I have a bookmark to the youtube subscription page, and have directly visited that URL 3 times via entry inside the urlbar.
With three letters typed, the autofill is still stopping at the base URL and not supplying the bookmarked and previously visited URL. The full subscription URL will not autocomplete until 5 characters are entered: