Although his sources to things outside of Smash are erroneous, it's what he says relating to smash that matters in this situation, as they're not all the same sources.
When it comes to telling us information on Smash Bros. Ultimate, he's been completely spot on and has yet to let us down. He clearly doesn't have the full story, no leaker does. But the bits and pieces of the story he does have are absolute truth, the only thing to my knowledge he got incorrect related to Smash wasn't even Smash itself. It was a Castlevania bundle of games to be announced for switch alongside Simon's reveal, and even then, we eventually got those Castlevania games for the switch.
I know of nothing else he could possibly have gotten incorrect when it comes to Smash Bros. Ultimate leaks. If he has gotten things correct, forgive me, and please tell me what they are. However, in this current point in time and to my knowledge, he's the most reliable source of information for Smash Bros. Ultimate we have and has a flawless reputation for Smash Bros. Ultimate in terms of what he has told us and how much of it was correct.