I'm of the opinion that "excessive" demething gives a minor reverse reaction, producing monoglycerides. These *may* be the stuff we call HMPEs - certainly in my testing they form hell of an emulsion with water that doesn't easily split, just cloud a 3/27 test without dropping, and if accumulated together over many batches can be successfully reacted into biodiesel with a little extra NaOH and Methanol.
If they were proper high melt point esters, then reacting again shouldn't really help much, but it does - giving FAME that can be chilled much lower without their re-formation.
All of that said, I've WBDed for years and don't intend to stop. It's a great process and saves money on the most expensive component - Methanol.