Regarding the new 5ch leak,
There are a few things that I find weird with the leak, but honestly I feel you could make an actual argument for Nakoruru and Velvet.
For both of them, it could be simply the case that they were aiming to get more female characters into the cast. Plus we actually have quite a different perception of some characters in the west which may not make some choices seem viable, but for Japanese they would make a lot of sense.
Nakoruru from what I understand is the most popular girl from SNK and Samurai Showdown is getting a new title, so she wouldnt actually be coming out of nowhere. Plus something that I dont know if it has been mentioned before here in the thread is the fact that at least in Japan she is seen quite prominently alongside Terry, as SNK founded a non-profit organization with both as mascots:
https://snk.fandom.com/wiki/Nakoruru_&_Terry_Club
For Velvet, you could that they wanted to represent the latest Tales in the franchise as a compromise due to Tales having several viable picks. Tales is a different situation compared to FF and DQ, as Tales most popular character depends heavily on the region for the most part, and also console somewhat. Yuri (Vesperia) and Leon (Destiny) are by far the most popular character in the Japanese character polls, they are so popular that they had to be removed from consideration as they pretty much dominated every poll:
https://www.siliconera.com/2017/06/04/tales-festival-2017-character-popularity-poll-results/ .
In the west, Lloyd is probably the most popular given that Symphonia is the most popular title here and he had a presence over the course of previous Smash games, but as shown in the poll I posted, he is not really that popular among the fanbase over in Japan with even Velvet coming above him. Yuri for better or for worse, didnt have that notoriety in the west due to Vesperia being somewhat locked to a console that wasn't very popular with JRPGs until very recently.
That said, the most notorious thing going on for this leak is pretty much the supposed poll results. While not saying that they are actually legit, the way they are presented seems quite plausible. You have several characters on it, some at the very top with really valid choices, some rounding the top 10 in popularity, some notorious picks on it. Plus having franchises listed in general instead of particular picks makes a lot of sense, considering a few franchises are in the situation of having several viable and popular characters on it so it would be more divided. Examples of this would be FF and Castlevania which were mentioned by Sakurai.
Results-wise like I mentioned before, there are a few oddities:
-the absence of Wolf/Star Fox unless the author forgot to include them for some reason
-it lists Okami instead of Amateratsu which is odd unless it also considered Chibiteratsu
-a few franchises that the author added afterwards
-the non-commital outside DQ content as Velvet, Nakoruru and the RE rep, were only mentioned as possibilities and nothing in concrete
Its an interesting effort if fake honestly.