You'd see the dot on the left side of the status bar if you had overflow notification icons. The dot on the right presumably means that there are overflow system icons (like maybe a Do Not Disturb icon, headphone icon, etc.).
That's one thing I hate with the new update. It makes no sense for phones that doesn't have the notch to still have a dot to replace extra notifications. I would assume the OS should be smart enough to differentiate a phone have a notch or not. Why take out the notification icon when the phone still has space for it?