Can anyone provide a citation for the existence of pre-alpha MTG rules about an initiative stat in combat?
Mark Rosewater, Magic's lead designer, says it's not true that such a mechanic existed. He began working with Wizards of the Coast in 1995 (the game launched in late 1993) and has been the game's lead designer since 2003. From his blog, Blogatog (on February 22, 2016):

gatvin asked: Back when MTG magazines were a thing, I used to get Inquest Gamer. In one of their articles, they showed some early magic cards and they had three stats. Power, toughness, and initiative. Initiative determined damage order in combat and later turned into First Strike for simplification. Now, as with many things written by people, they were sometimes wrong. Do you know if that was true? It was weird to not hear anything about it at all in your story about the design of Alpha.
Mark: To the best of my knowledge, that is not true. The Star Wars TCG we made did have an extra stat for Speed. And yes, in our game Han was faster than Greedo. : )