Yeah, I’m not entirely convinced it is true, although will point out that Marts is one of the (renamed) people in the podcast story, likely the editor knowingly hiring “Yoshida” and involved in the “Six Gun” thing also mentioned.
As for the implications if it is true, well, it’s more than just circumventing an internal rule (a good one, I think, but that’s neither here nor there). “Yoshida” would have been pitching against outside freelancers for Marvel projects that he wasn’t supposed to be able to work on, with inside knowledge of what the editors in question were after, let alone that one or more of them may have been knowingly hiring their colleague under a fake name against company policy. He specifically mentions having to pitch against other writers for the Age of Apocalypse series, which I imagine is easier to win when you work in the same office at the guy you’re pitching to. It’s not a great look. Plus, if the rest of the company didn’t know Yoshida was a pseudonym, then the cheques were being written to a man who doesn’t exist and supposedly lives in Japan, but cashed in America, which seems slightly dodgy.
Also of note in that interview, “Yoshida’s” past work experience is all conveniently vague (Dreamwave series that never got published, editing for a Japanese manga title that got bought out by a bigger publisher) but lines up with Cebulski’s pre-Marvel work (editing manga in the US), including working with Kia Asamiya, the person who supposedly introduced “Yoshida” to editors at a convention (despite, in the podcast, everyone only ever having claimed to dealt with Yoshida via email and never having met him in person). The span of “Yoshida’s” Marvel writing career perfectly lines up with a gap in Cebulski’s writing bibliography and also the time-frame of the Jemas instigated rule of editorial not doing freelance work. And, frankly, from the quotes he sounds like any other American comics writer.