Slow near any 3d object

Unity Engine
1

Guys, this is noticeble only on mobile.
You can create an empty scene, put a 3d object there (cube, sphere, etc). If you get near enough, you will notice the game lags, decreases the fps. Why does this happen? You have to get near to the point it will cover the screen.

This happens even if you try to increase game performance (using only baked lighting and baked gi, or even mobile shaders).

Thanks in advance!

2

There is a potential reason.
Cover area of transparent triangle will drop FPS heavily.