I really don't get what WOTC is doing with front side's first loyalty ability. To be clear, I don't dislike what it does. What I dislike is that there's no built-in tool to track the effect on that creature.
By comparison, Kaya the Inexorable's first loyalty ability is
+1: Put a ghostform counter on up to one target nontoken creature. It gains “When this creature dies or is put into exile, return it to its owner’s hand and create a 1/1 white Spirit creature token with flying.”
Notably, with this ability, the ghostform counter does nothing mechanically. Whether the creature gets the counter at all or gets multiple doesn't matter. It's only used to track that the creature also gains that additional ability.
They could have easily done something like this with Oko. For "until end of turn" abilities, it doesn't matter that much since you don't need to track it anymore after cleanup, but for permanent abilities, it can be easy to forget in a few turns which creatures you've used the ability on.
One other card that works like this mechanically is Chance for Glory, but this is what that card says:
Creatures you control gain indestructible. Take an extra turn after this one. At the beginning of that turn’s end step, you lose the game.
Despite that the creatures permanently become indestructible, the game is intended to end on your next turn, so you shouldn't need to track it for long. (Yes there are always exceptions but the intended use of the card means you don't have to track it for long.)
