Does anyone know how to remove this? I just wanted to add smoothness to the models, but not that.
The split faces subdivided look a lot like what a quad would if subdivided. Thus as @Rekov already mentioned, you should be fine after doing the following:
- Deactivate the Subdivision Surface Modifier (faster depending on the model)
- Go in Edit Mode
- Select all elements of the object with A, either mode, vertices, edges or faces will work
- Press Alt+M and select "Merge by Distance"
- Go in Object Mode and if you did not do yet, RMB Shade Smooth
- Activate the Subdivision Surface Modifier again