Not autistic, but ADHD, which comes with rejection sensitive dysphoria, which does affect how much we "allow" ourselves to be emotinal/vocal in meatspace.
Yes, there are definitely system members who don't emote well, or even talk, when they front. Part of it, I think, is some people have "issues" they need to sort out. Sunny is incredibly anxious and scared, even though there is no danger anymore, so she can't do much more than be frozen in place. So we need to work with her and get her to understand she's safe and trust us.
Another theory I have is that some people aren't as used to driving the body, so emoting/tones/speaking is difficult because they just don't know how to operate this thing. For "the body" in this context, I am including part of the brain, because there is some sort of interface/filter between what you think and what you do. Because of the ADHD, the body deals with auditory processing issues, which means our hearing is pretty much perfect, but speech being converted into words our brain recognizes just...doesn't always happen. And I, as the host, am really aware of this issue and what I can do to work with/around it. But the others really don't, since they don't front as much. And that can be remedied by them fronting more (or co-fronting? and taking notes) and learning how to work the body better.
So maybe your tone/speech/emoting issue is rooted in the fact that there's some (metaphorical) button or knob the fronter has to hit to make it work, which you don't need to do in headspace, but since you (the host, presumably) do it so much, you don't even think about needing to do it anymore. But the others don't even know they're supposed to be doing it.
