Gas I don't think any of your last comments apply. I'm sure to safeguard MVT members it's just a case of get a licence anyway as there is no fee involved. I expect the tour leaders would not want the embarrassment of answering questions if they had got it wrong. Especially regarding the different border rules that might apply after Brexit, which is likely before next June.
As a private individual traveling to Normandy next year, I'm quite happy to ignore the whole thing, but if I was in charge of a large tour I might want to be doubly sure.
I wonder why they saw fit to exempt France, Belgium and Germany and not also the Netherlands for instance?? The older than 50 historic vehicle doesn't come into play in other countries???