>>719798946
People definitely look into some things too much
But that specific line of thinking comes from Undertale, where in the Genocide route your character starts moving (or not moving) in cutscenes where they would normally go along with whatever wacky bullshit is going on. It becomes notable because you have what normally happens as a point of comparison, and by the end of the route it progresses to the point that they take over the initiative and kill the final enemies in the game all on their own.
In Deltarune it's different but also more straightforward, because You the player are unambiguously your own thing that is controlling the main character Kris who has their own agenda. Kris can still say or do things on their own while you're "controlling" them, but they'll also sometimes try to resist what you're making them do to the point of physically ripping you out of their body and trapping you somewhere so you're suddenly stuck wiggling around in a box while they're doing their own thing in a cutscene.
There are things that people read into too much but there is a real and important distinction between the player and the "player character" in these games.