Well for one, >>106614259
was posted (and later deleted) by John Mangor-Baurley, a technical director who might not even be working on Amphibia specifically. He also shared pic related.
But the Smash Bros. photo was from Matt himself; it’s possible that the series creator gets a little more leeway. Plus, unlike Mangor’s Toad King photo, what Matt shared probably isn’t as big of a deal since (1) they’re just background designs instead of an unrevealed secret character, and (2) said backgrounds are obscure and not that clear to begin with.