My September 2017 visit to GP Gliders

You probably have reasons to be skeptical but, they should only "expect" until the validation (ground/flight tests) are performed and don't force design changes.
If they updated their configuration this year, it makes sense for the validation tests to happen in Q1 next year.
Because this is not a complete redesign, they should be confident enough to pass validation tests and take the risk to start production using new configuration right now. Therefore I am not surprised to hear they are updating already produced gliders and produce new ones with latest configuration.

"wasn't design driven, but regulatory driven, meaning it can't be relied upon"
I don't get your point, the same situation would be true for anybody designing under FAA/EASA or UL. Until you apply for TC, if authorities changes the rules, you have to adjust.
The UL regulation changes in EU took a long time to get delivered and I am confident it is going to be stable for quite a bit of time.
GP did their best to come up with design targets and now they adjust them to fit most authorities requirements.

Concerning the MTM, if the structure is not the limiting factor, GP will eventually have to adjust it to pass the Vso requirement for UL in EU (i.e. 45 Kts for Germany and 38 Kts in France).
If structure is capable, US experimental could use a higher MTM but, who want to fly above 60 kg/m2 anyway?