When someone puts it that way, it's hard to argue against it...
Unless of course you want to say that these "sporadic" speed changes are made for the sake of gameplay, with less emphasis on realism. As far as I am concerned, gameplay is #1 while realism must take a sidestep.
We should accept that a lot of things in SH3 are not the way they are in real life, but that is due only to the limitations of a videogame; an imperfect simulator. So in that regard there may be unreal discrepancies between SH3 and reality, but that should be the way to go, rather than having a realistic but unenjoyable game.
And if I am not mistaken, I think Der Teddy Bar's primary intention was to improve gameplay with this mod, at a secondary cost of losing a little bit of realism. I am totally fine with that.
As a u-boat kaleun, our only task is to locate the convoy, and sink it. And with stock SH3 settings, that is way too easy to do.
So if you haven't already guessed it by now, I completely agree with Der Teddy Bar's sporadic speed changes, no matter how uncommon this may have been done in real life. Now, locating a convoy in SH3 should prove to have an increased degree of uncertainty and difficulty.
I hope some will agree with me...