We know Chara has power in them, and they’re a currently red soul. The alternative is that kris didn’t have a soul before, and if they’re given a fully original red soul, then maybe the reason the SAVE and the soul type are the same name is to further prove they’re the same thing. And as I already reasoned, soul color change is something that does happen ingame and very likely happened to Kris. with it’s huge connections to the angel’s power and the player’s control, it feels like it’s not normal. They say it’s Your power, your soul and dt brought them back -but they mention power twice and in one of those directly that it’s the power that brought them back. Really, at the end of the day I just think the unnaturalness of the red soul is enough for me to be hesitant that it’s natural to Chara. Each soul trait that colors your soul gives you a new ability, I don’t think it’s a stretch that could be extended to a unique SAVE power. the other humans had determination, yes, but clearly not enough to control the timeline to such a degree of flowey. I think the SAVE function is just an extension of the soul. I think all souls are capable of having traits of the other souls -monsters are able to turn you blue or yellow ect., and while that could be unique to red souls as you need to collect all soul types in the ball game to get to red, I still think it’s placement with the flowers is enough to push me to saying its the traits. The golden flower is placed among the other flowers, that implies it’s with the other soul types.
Oh! i talked about this a bit but I could elaborate more on that.