We do think that the mantle could actually act somewhat like a conveyor belt and it that is a good analogy, then there should be mantle plates traveling along the underside and this seems to possibly confirm just that.
All that we see suggests a strong equatorial band of direct activity. It could provide a plausible understanding the whole of our geological history and is well worth exploring.
We are now reaching a critical mass of geological data gathering that may well lead to new revelations. Curiously my crustal shift conjecture is actually becoming far less tortuous as well and fits in well to all this.