I think I’ve had so little experience with fluent speech as a stutterer that the word generator part of my brain doesn’t know how to properly function when I’m speaking. My body can be so focused on HOW I’m speaking that it can disregard WHAT I’m saying, if that makes sense. On top of that, i prefer to just get my point out. That usually means skipping over the words i want to say but can’t bc of the stutter and jumping to closest word w/ a similar denotation that I can actually say. I’m sure there’s more that factor into it but this is just my 2 cents lol. It may not even be scientifically accurate but this is how it feels to me :)