Thought I’d lay out some of the foreshadowing I’ve been doing about this plot point...
First there’s Chara’s Asriel “halucinations”.
I bet they make a lot more sense now.
In the case of the second one, the two parts of Asriel’s soul are so close in proximity that Flowey started acting unusually Asriel-like. You’ll also notice that he started to show a goatlike nose in this scene which is gone immediately after Chara leaves.
Another small visual cue I’ve been doing is that whenever Chara thinks about Asriel, they have this habit of clutching their chest… as if their heart hurts.
Here’s one where Maverick said that he’d missed Chara.
And here’s one where an asker insinuated that Chara didn’t care about their family and they angrily objected.
And here’s one where an asker basically said the same sort of thing that Asriel has been saying to them “There’s good in this world and there’s good in you too.”
They are unconsciously doing this because whenever Asriel is brought up, they are slightly made aware of the effort it’s taking to hang on to Asriel’s soul. It literally hurts them, but it’s constant so they don’t usually notice it.
There’s also the fact that you can literally see Asriel’s soul with the speck missing from it right there inside Chara’s soul whenever I’ve shown it.
So now you guys understand why that soul speck never grew. It’s because it was never a “seed”. It was a shard. A tiny puzzle piece missing from the whole. Flowey gained it when Chara was booted out of Sans’ mind. Sans had weakened them considerably, so a tiny bit of Asriel was able to break away from the whole and lodge itself inside the only body that it made sense to hang out in. It may even have been an intentional seizing of an opportunity on Asriel’s part.
Maverick, of course, already knows all of this.
He even tried to hint at it with that jumpdrive of his.
But he can’t risk telling Chara about it directly. He doesn’t even want to tell the askers because you could easily tell Chara about it. He’s worried that if Chara knows that Asriel’s soul is inside theirs, they might never let go. He wants the Asriel of this world to have the second chance that he was given.
He’s not the only one who knew all this from the start..