Sometimes, I put a little extra thought into a comment and I think, "Hmmm, I should turn that into an entry on my blog." This is what happened here. David was discussing The Avengers #33, and I pointed out the mistake on that issue's cover was corrected for a reprint of the story in Marvel Triple Action #25. This led him to ask the question which is this entry's title. Here is my (re-edited) reply:
That's such a good question that I don't have the real answer for you, and don't know if there's ever been one offered (seriously). All I CAN say for certain is how the title was marketed:
1) The first few issues reprint Fantastic Four stories, but are promoted as starring the Thing, Doctor Doom, and the Silver Surfer. The first issue promises "3-in-1 Thrills!"
2) When the book shifted to the Avengers (the FF usually was reprinted in Marvel's Greatest Comics), the three "stars" were Captain America, Thor, and Iron Man. This was fine until you get to The Avengers #16.
3) Eventually, the book was sold as just an Avengers title, but usually with three "bursts" touting stars. On #25, they are on the right of the logo. I doubt anyone bought the book on the basis of things like "Goliath and the Wasp!", but they kept up appearances. This practice was dropped in the last year of the book and they just ignored the fact that the title made no sense.
4) There was one period when the MTA name DID make sense, and that was ironically when it was briefly cancelled. It resurfaced as Giant-Size Marvel Triple Action and reprinted the Avengers, Daredevil, and Dr. Strange. The ongoing Giant-Size books were ended and MTA resumed its original numbering as an Avengers-only book again. Coincidentally, the first post-Giant-Size issue was #25. So yes, the story is "continued" from Giant-Size Marvel Triple Action #2.
Finally, to wrap this up, here are the GCD cover galleries for Marvel Triple Action and Giant-Size Marvel Triple Action.