I'm with you on this.
I have 2 pairs of 107 and one is much smaller than the other one, specifically in my case one wash are smaller than two years wash.
Now, thanks to various lockdowns, I had to to size up to a 4 and again same size doesn't fit the same across the range. Black ones I recently got are much smaller in the waist.
What you mean with EU issued pairs? How you identify them?
Only thing I can think of are those pairs with some Elastane in them
Recently I've checked measurements on various sites (Tenue De Nimes, Cultizm, Meadowweb, Frans Boone, End, The Bureau, MrP) and it's a nightmare. Rarely I've seen such inconsistency