Howdy,
Reading your issue, I thought this might be an issue where the Mac was interpreting your pauses as the end of one sentence and the start of another, thus capitalizing after the pause. (Although it looks like it is inserting commas instead of periods, is that a hint?)
However, I was unable to duplicate the issue even with all the autocorrection I could find enabled. I tested with TextEdit, Pages and Notes, turned on "Correct spelling automatically" and "Capitalize words automatically" in System Preferences > Keyboard > Text and in App > Preferences and under the Edit Menus > Spelling and Grammar, with Grammar correction on where available. I couldn't get it to think a pause indicated a new sentence. I tested with Keyboard Dictation as well as Voice Control Dictation.
That said, what happens if you turn off those autocorrection features? Does it still capitalize after a pause?
ivan