This is the first I've heard an inkling of a problem. We've been tying Dyneema for 30 years or so now haven't we? I concede that a loose bowline could come undone if it is not "set" correctly, but that is user error, and nothing to do with the the knot or the rope/line. Just set the knot correctly and keep it simple. I do like the idea of the Dog and Bone holding a spliced loop though, but can see also that it could shake itself loose.