papagenos
has a source he 100% trusts, whom has a Microsoft source who has seen proof of Banjo. Among that, the Microsoft source and his source have heard of Chorus Kids, Mach Rider, Geno, Isaac, Shadow and Ken, as well as Isabelle and Incineroar (the last 3 being known apparently way before anyone knew; months ago), but had no substantiated evidence like Banjo did for them. However, Ken was allegedly leaked and Isabelle was revealed.
Additionally, the other 6, including Banjo, were shown in this leak, solidifying that they may have been right.
The only thing confusing to Papagenos and his sources is Incineroar, whom other insiders are claiming as well. We don't know if Incineroar was fake-bait to out leakers or if he is DLC. Additionally, Spawnwave is seemingly against the leak, but only because it's missing Incineroar and another character, believed to be Sora.