On s21. One app I use to look at all my other apps says all my pre installed factory apps were side loaded. I tried to register but I never got a confirmation email.
Welcome to the forums. Which app is that? It's possible that it's labelling as sideloaded all preinstalled (system) apps that can't be updated from the Play Store.
What app are you using to look at the other apps? I would guess that it's a flaw in that app, which is mistaking preinstalled bloatware with sideloaded apps.