I love this song, always have. The solo is one of my favorite of his, and he really does a great job on it live here. I never knew how he did that upper fret lick. I see it’s a wide stretch thingy like in “Beat It”. I’d almost prefer not to know.
Anyway, the truth about the scale part is that it’s just a vanilla ascending six-note scale fragment, straight up the scale. He sometimes plays it with strict alternate, starting on a downstroke, i.e. dud-udu. You’ll see that in the upper octave in the first YT clip.
But in a couple cases here, he goes down-hammer-hammer, and then does dudu on the next string even though he’s fretting only three notes on that string. In other words, the pickstrokes do not line up specifically with any particular fretted note. He wants to do those four fast picking movements on the string, ending on the upstroke, because that’s how he feels it, so he just puts another pickstroke in there. Maybe certain pickstrokes line up in certain takes, and others in other takes. It varies. We’ve seen this in players we have filmed. It’s a thing people do, again mostly by feel. It is what it is: four pickstrokes on a string without a specific connection to the fretted notes.
If you want to practice dhh-dudu with synchronization, you can write plenty of phrases that will fit that, picked note for fretted note. Or you could even modify this song to add in a passing tone and make it match up. That’s up to you.
Still great playing and still great song.