To be clear, they never used the term "clone" either, which keep in mind clone is not what an Echo refers to. An Echo is strictly a fighter who does not have their own regular number and has the same proportions as another character, using them as a base while having a similar moveset, sometimes almost identical(with often barely any gameplay differences that matter to boot. Do note that they will have a bare minimum of unique taunts and some slight animation differences that can barely affect gameplay too. Those are the lowest effort ones). Sakurai stated that Pass 1 will not have any Echoes.
Clones use a character as a base, but can be wildly different. They still resemble the character. The ones that are the most different are often not labeled a type of clone either, like Ness, who directly used Mario as a base(but got changed up so much you can't even tell anymore after Smash 64). Jigglypuff is similar, but you can tell she's still akin to Kirby. Wolf is an interesting example as that he barely resembles Fox outside of the specials. Whereas Luigi, Jigglypuff, and Captain Falcon more resembled their counterparts(Mario, Kirby, and Samus) closely in comparison. The bigger similarity is the same series.
People don't expect a regular clone, or semi-clone for the same reason as an Echo. Since we're paying full price for that and other content, they expect "pretty much unique". They still clearly often use others as a base either way, but that's just to help start 'em. They aren't meant to be similar to another character. Hero is like the only one that resembles someone, and it's not clear how if he directly used Link as a base or just borrowed some animations specifically. Min Min used Falcon as a base, but they're nothing alike from what I can tell other than an animation or two. I'm likely just not noticing some stuff or it hasn't been talked about enough for me to know.
Technically speaking they could include an echo/clone/semi-clone in Pass 2 and it'd be fine. They didn't say anything about them being barred. There's no false advertising. But it's pretty doubtful as Pass 1 set a precedent. However, seeing as how we just got a Spirit now playable, I wouldn't put any stock into "expectations" in itself.