I've noticed similar things with GWX.
It's a wonderful mod, but the AI is tuned too heavily in favor of the enemy. For a mod that boasts ultimate realism it seems pretty strange.
From everything I've read about uboats 1939 was a Happy Time, yet in GWX the escorts can sniff you out remarkably easily- which is not to say their depth charges will actually find you, but the ease at which they detect you is nuts. I guess it forces you into using more sound techniques and strategies to attack convoys, but in the end I find it unecessarily frustrating.
In particular, what annoys me is how easily a destroyer will spot my periscope or pick me up with hydrophones before I've even attacked a convoy. They have no reason to be so alert to the presence of a submarine unless they already know there is one lurking around.
I could understand that sort of behavior in 1943+ but in 1939?
Why doesn't the GWX team bring out some kind of Easier AI optional mod that can be installed with JGSME?
Seems to me that would make the game more enjoyable for a lot of people.