Phill, as you will know that is a French car and I believe the German authorities also allow this no matter the age of the (Morgan) vehicle as the trailed item also has to have an MOT.
I don't understand the logic either.
Here there is an age limit, ironically after a certain age (I don't know the cut off) Morgan's were no longer allowed to fit a tow bar.
A great shame for people that enjoy this kind of touring whilst having a great car for unhindered exploring, I know Tim has an earlier car hence my comment.
Piqued my interest, It's all about type approval for the towing equipnent (I.e towbar securing points, weight limits etc,etc), and I guess the reasonings behind it are reasonable, principally manufacturer cost to type approve.
I guess I'll take a tent, or glamp if we get back to Boardmasters again

Either that or buy an(other) earlier Mog!
From The Ministry
"If your car was first used before 1 August 1998, your tow bar doesn’t need to be type-approved."