There is some otherwise-unheard-of lore in those books, but it's extremely unclear if it's actual lore. I'll explain why.
Basically, they were written by Nadia Oxford and David Oxford. They're known in the fandom as Red Draco and Black Draco/Nytetrayn respectively, and have been around for a very long time. They're a married Jewish couple who live in Toronto, Canada.
They're actually nice people, from what I understand. Just weird. Nadia Oxford posts under her real name on Twitter. The problem is that she does this kind of thing where she intersperses her Mega Man content with talk about, say, her (shockingly not homosexual) smut Final Fantasy 6 fanfiction. In other words, there's no separation of the two kinds of thing. This is why any lore in the Field Guides is questionable at best: how much of it is real vs. a fanfic. Aside from MM, she's done liner notes for some Breath of Fire vinyl record thing.
Nytetrayn has, to my knowledge, done only one weird thing. He uses his MM website, which used to be one of the larger ones, to promote his MM Legends prequel fanfiction, Legends of the Halcyon Era. It's, as you might guess, rather sexualized, including a guy stripping in front of a kid character named Radi. Again, the issue here beyond the content is the whole "why are you showing this off in public, on your website's Twitter account, which is easily tied to your IRL identity?"
This gets more suspicious when you find out he commissioned "cover art" for that fanfic from an artist known as VSpyren, also known as VCampan. Why is this suspicious? VSpyren has at least some months ago reportedly been in the middle of doing lolicon of at least Palette, and I seem to also recall being told they drew Roll in that manner as well. Does Nytetrayn know that? I cannot say.
So yeah. The writers Udon gets for MM stuff are a tad questionable, and if they're involved I'm not convinced they can keep it professional/clean.
