I don’t think this is bug or anything, but when I start new file, everything is OK. After about 5minutes of working when I go to example side view, objects look different. When this different view comes, everything is 3D even in side view.
To explain better, here is a picture:
There’ll be a reason you just dont know what it is yet .
In your 5 mins of working with blender, are you going into camera view and then rotating the view, that would leave it in perspective mode.