Weren't there only three secret characters (and Jigglypuff) in Brawl with Wolf, R.O.B., and Toon Link? They definitely are taking a different approach than that of Sm4sh, but that's not to say that Brawl is much different in terms of secret fighters.
In fact, I'd say Ultimate is far more different than either in terms of marketing campaign because first of all we only got a "proper" reveal of the game six months before its release, that's actually more in line with how Melee was treated. Secondly, we were shown every single returning fighter in its first reveal; for both Brawl and Sm4sh we didn't know every single returning veteran until the game launched (leaks aside).
This marketing strategy is far different than what we've seen in the past, so I think honestly we can't judge exactly how they'll market it until we see more content from Nintendo. Having the announcement trailer and the E3 presentation honestly doesn't tell us a whole lot, except for the fact we have a far shorter "waiting period" compared to past games, and that we know all of the returning veterans. Those two facts in of itself separates it from past Smashes.