does support synonymy...but it is strange that this insect is considered to be Agonum decorum! It is very different, pubescence wise.
And I know, because I used it quite a bit, that "Illustrated Identification Guide to Adults and Larvae of Northeastern North American Ground Beetles (Coleoptera: Carabidae)" by Bousquet does not mention that A. decorum could have pubescence OR NOT.
Bousquet uses setae and pubescence a lot in his keys.

Can you follow what I am saying here, with my special english? To me this insect should have a name on its own!

my limited experience with carabids & carabid literature suggests that the intraspecific variability can be massive, including noticeable differences in aedeagi in widespread species; sometimes it takes a huge amount of material from the entire range to decide what's going on and how things intergrade [or not]...
having patchy echantillons from different spots is exactly what has resulted in seeing more taxa than actually exist; that's how we ended up with laundry lists of synonyms in way too many cases, and with all kinds of rather shaky subspecies, 'races' and what not (the situation in Cicindela is a good example; further research is expected to invalidate and dismantle the entire intraspecific structure; i anticipate a backlash¹ ))))
that's why the state-of-the art revisionary work involves studying tons of material and often results in complete reassessment of earlier species concepts even where least expected.
you should really talk to someone who has intimate knowledge of this group.
[i see no problem following you at all, but feel free to write me in French offline]