multi spark ign. vs timing light.

I have a cheap HF dialback I got when my Craftsman finally died and I was wondering the same thing. I borrowed 3 other timing lights from my dad (Craftsman, Actron, and Heathkit I made a long time ago) and all 4 read the same with the MSD on my Barracuda. I agree with Moper, I don't think it is age but the actual way they process the signal.