As most of you know, I am an avid 5 string player. I also have been using the floating thumb technique almost from the very beginning of my bass playing, including through the B2B course.
Today, I stumbled across this old Mark Smith video in which he talks about transitioning from 4 string to 5 string, and some of the pros and cons thereof. About 3/4 through the video, he talks about the floating thumb technique, which IMO (and Mark’s) is essential for muting on a 5 or 6 string. He also points out how much better it is for the wrist. If I ever go back to a 4 string, I would still use the floating thumb for that very reason.
I know some people have asked about playing 5 string, so maybe this will be helpful.