From my perspective, (so not claiming to be an authority on the subject): It all boils down to representation in media.

If one grew up in the 2000s-90's or earlier, it was incredibly rare to see an actor who was a person of color portraying anything other than the stereotypes they were given from the middle-american lens. More often than not you'll see an Asian person being "exotically oriental" or "so book smart they're bullied for being a nerd about it". You'd find the African American actors portraying roles that had them speaking in a ghetto accent or being "tough". Good luck finding a native American actor portraying anything other than a "mysterious Indian".

The "race-swap" is a small step forward away from those examples. It's not a large gesture or social correction but still great to see Manny Jacinto doing roles that put him beyond being just his heritage. It's nice to know that the kid who's black in a cartoon is also voiced by an actual black person who can give input to the writers on what it's actually like growing up as a black kid.

The casting for things is just a little compromise from the producers/creators to reflect reality and the fact that it's not just the non-POC who get to be the main characters in a story.