This is common but highly dependent on picking style. In pretty much any USX style, this doesn’t happen. It’s DSX and mixed escape players, especially wrist motion, where you see this. Yes, Andy does this on the low strings.
The most straightfoward solution is to track via upper arm or elbow, in addition to some small amount of wrist tracking — not so far that you hit the edge of your range of motion and kill your efficiency. If you don’t like sliding the whole arm, then elbow also works. A very small amount of elbow motion is enough to relocate the picking hand to the lower strings with no change in forearm rotation.
We can see in Magnet footage that players will often try to “reach” to the lower strings through some kind of finger adjustment. Check out Wim Den Herder’s “Mad Max” from bar 5 onward in slow motion and see if this what you’re referring to:
If this is what you mean by “thumb bump”, this can work, as Wim demonstrates. However it seems to work best when your whole picking motion is to some extent finger-driven, like Wim or Martin Miller. You’ll also note that Wim doesn’t do a lot of upper arm tracking — it’s mostly elbow, wrist, and the finger stuff. While there is some of the occasional rotation you’re mentioning on the lower strings, he’s able to avoid a lot of that on the biggest six-string jumps with a little elbow.
Where it seems less ideal is when your picking motion is some other joint (e.g. wrist) but you’re just adding in this extra finger adjustment to fix a problem that only occurs in specific places. When we see this in Magnet footage it just seems to correlate with errors like missing notes especially during complicated string skipping / roll patterns / etc.