First,
I have had the pleasure never to actually have to play the stock SH-5 campaign and, in fact, did not consider buying it until I read about this campaign enhancement getting rid of the terribly arcardish vanilla campaign.
But I have come across some oddities in my first campaign, which is now in December 1939, that I believe are related to this mod.
For instance, I once engaged a convoy in the British coastal area some time in October '39. It was unescorted, which seems right for this period, but almost all of the (merchant) ships in it were heavily armed which does not seem correct for this year. Also it had some Liberty-freighters in it, which I believe didn't exist back then.
Another thing, I just recently encountered a single Iclandic(!) passenger ship coming from Iceland going to England which kinda made me chuckle, since Iceland didn't even exist as a sovereign nation in 1939. Since it was also armed I naturally saw through the British ruse trying to confuse me with some fantasy flags and promply sunk it
It was, btw, a Uekel small passanger ship. I seem to encounter an awful lot of these everywhere. Very few freighters as lone merchants but many many of these little buggers.