Pixel-perfect isn't gonna happen; there are at least 3 different eras of card that the generator averages between, meaning that it no longer produces a 1:1 image that matches any one of them. It DID match movie era pretty darn closely early on, but after being met with the differences I decided to pick and choose whatever standards maximized card text area.
The twilight shadow in this case is actually for improved visibility; it's not so big a deal on the printed cards (which of course was Decipher's main concern), but on digital screens the contrast is not very good. That said, if you truly want to be a purist in this area (and are okay not being a purist in things like game text margin), then you can apply a hack by editing around line 350:
Change each of those "0.5%" to a "0%", and each of the "0.03" to a "0". I would encourage you to do a before/after comparison and decide if it is actually an improvement. (Also note that this will affect the drop shadow on non-twilight numbers such as Strength, Vitality, etc. If you want to keep those, alter the lines that reference "twilight" and keep the ones that reference "numbers").
(Also, you'll need to reapply this change any time there's an update, just be advised.)