Some of the logic.
When Sophie did her doctoral thesis here, (tagging etc) she learned that BIGGER spawners had a higer return rate. By C&R the +14 inch sea trout, we hope to get a better multiple return rate.
The egg producing capacity of the big females is also proportional to their size.
Thus, why not let males at any size be taken, ... well, in early summer, it's hard to tell 'em apart and we don't want ambiguois rules. Also ,... maybe bigger fish spawn BIGGER offspring, so we'll try. Do BIGGER fish have a really better gene pool for long term survival? ... don't know as size is really just a phenotype.
Still ... better than no protection.
On the anglers' side of things, the daily quota USED to be 3 of any size. Seeing as some of the limited rods zones are pricey, the angling experience should be better (we still have lots of C&BBQ anglers).
Sorry, I can't find any of the supporting documentation in English, ... if you want to brush up on your French, I'll post the links