Although I haven't tried this pup nor the SD '78, I say, "pure hype".
I'll bet you'd get very close results (just pickup-wise, mind you) using a good vintage-output PAF repro.
I was on a board once where every other topic was "Eddie Tone This" or "Eddie Tone That"... some info was interesting,
some was pure BS. Even Terry Kilgore chimed in with his knowledge. The thing that most seem to forget when it comes
to getting the "Brown Sound" is the stuff Ted Templeman did in the studio; esp. on the 1st album.
Personally I think it's kinda cool. If it's the same PU they're actually using in the $25K EVH Frankenstein, and Eddie's swears the reproduction is basically idenitcal to the original, then... cool. Hype or bullshit, who knows. It should end the debate about which PU to choose if you're ever making a frankenstein copy.
What did he use originally? He's known for his licks and tone (or overuse of effects), but his early guitars always struck me as a "I'll grab this and make this work" kind of thing. They were (literally) stripped down to the bare essentials. Even his Kramer that he "designed" consisted of him visiting the factory and looting unfinished parts that he assembled later. So a pickup to his exacting specs, what does that mean? Did he spec one originally, or did he just grab a Gibson hum and throw it in there, and this is that one?