It has little to do with authority and more to do with the effort/return ratio. Visual edits are expensive and dialogue changes are cheap, so it doesn't make sense to redraw frames just for an irrelevant onigiri.
4Kids was very well known to visually change the japanese shows they imported if they thought it was worth it, mostly in the context of censorship. For example, all guns and cigarettes where removed from One Piece, turned into toy guns and lollipops instead.
The most infamous example, however, has got to be Yu-Gi-Oh!. Yu-Gi-Oh started as a horror-ish manga about a trickster god forcing people to play assorted games and cursing their souls when they inevitably failed to defeat him. The game-of-the-week format eventually solidified into the characters playing one single game, Duel Monsters (the Yu-Gi-Oh! TCG itself in the real world), and the horror-ish aspects faded away, although they still remained part of the show's aesthetic, based around Egyptian human sacrifices and oddly-card-game-obsessed ancient cults.
When the manga was adapted to the screen, it started directly with a softer tone[1], especially because the show was to be a vehicle for selling cards in the real world, not dissimilarly to Pokemon and MANY other anime from the era.
Nothing that happens in the show is particularly crude or shocking, it had that kind of soft edginess that fit well with its intended target audience (early teens). I imagine watching Bambi had to be much more traumatizing than anything in the show.
But that was still not enough for 4Kids, which had a pretty aggressive policy of no violence or death. Kind of problematic when the show's main shtick was "Comically evil villain puts our heroes in a contraption that will kill them if they don't win." (You can imagine the frequency these traps actually triggered neared zero).
To solve this, 4Kids invented the Shadow Realm. The show, thanks to its occultist theming, already had examples of people being cursed, or their souls being banished or captured. 4Kids solidified these vague elements into the shadow realm as a censorship scape-goat. Any reference to death was replaced with the shadow realm. Now, one might wonder why the censors thought that "hell-like dimension where your soul wanders aimlessly and/or gets tortured for eternity" was in any way less traumatizing than "you'll die", but I imagine it's because there was always the implication that people could be 'saved' from the shadow realm[2] by undoing the curse.
The Shadow Realm was a massive part of the western Yu-Gi-Oh mythos and even today it's a fairly common meme to say that somebody got "sent to the shadow realm", which makes it all funnier that it is not part of the original show.
A couple funny examples off the top of my head:
- Yugi must win a match while his legs are shackled. Two circular saws, one for him and one for the enemy, are present in the arena. They near the two competitors as they lose Life Points, with the loser destined to have their legs cut off.
In the 4Kids adaptation, the saws are visually edited to be glowing blue, and it's stated they're made out of dark energy that will send anybody that touches it to the shadow realm.
- A group of our heroes fight a group of villains atop of a skyscraper with a glass roof. In the original version, the villains state that the roof has been boobytrapped so that the losing side will explode, plunging the losers to their death by splattening.
In the 4Kids version, the boobytrap remained, but the visuals were edited to add a dark mist under the glass, with the villains stating that there's a portal under the roof that will send anybody that touches it to the shadow realm. This is made funnier when the villains lose and they're shown to have had parachutes with them all along, and they are NOT edited out.
[1] Technically speaking, there was a previous adaptation that followed the manga more closely and got only one season, generally referred to as Season 0.
[2] It does eventually happen in the anime that the heroes go in an alternate dimension to save somebody's cursed soul. Obviously, this dimension was directly identified as the Shadow Realm in the localization.