I’m not entirely sure the thumb movement thing is something you can just do by moving the thumb. Rather, I think it’s a consequence of the lines a guitarist plays, usually with economy and sweep picking as the basis. It’s a testament to how effortless and inuitive Yngwie’s system is, that his body seems to just know to use the smallest, most delicate joints and movements to produce insane speed and tone when given the proper environment of pickstrokes and note choice.
I took a lesson from Jon Li years ago. He’s a death metal guitarist (or was?) and uses primarily economy picking or at least did when I knew him. In person, it appeared as if only his thumb joint moved. At the time he said something to me I’ll never forget: “Do you really think any of these players think about these things?” We were talking about Eric Johnson and circle picking.
I responded no, but I didn’t believe it. It took years for me to realize he was right.