It makes a lot sense, but we usually 1) don't notice the pattern and 2) we ignore things. For example, about the first, maybe the pattern is the volume. I have more problems if I talk louder. Notice you need a volume talking with one person but more volume for a group. About the second, the brain is tricky. Most stutters have problems talking to a person and worse to a group (and presentations), but no problem talking to themselves, pets or the wall. It's because the brain works different despite you don't notice it. For the brain, it's a different deal if you're talking to a different human being (and you're not psychopathic, of course). Maybe you managed to abstract yourself, when you're doing presentations, similar as "if you were alone" (Good for you, it's almost impossible to do it voluntarily). I managed, with little success, to do it but for random people, however it's not possible if those persons are something for me (anyway, do it with those people wasn't been healthy anyway).