Stretched On Stage?

I wonder why some pros changed their res from native to stretched
TenZ and zekken for example, both players usually play on native and they changed to 4:3 on stage
MiniBoo too, was on native before and changed to stretched on stage and what made me ask that he streamed today and he's back on the native
so what is the matter with the stretched on stage?

low fps

It it's normal on Stream it's because stretched looks terrible on streams. You also have to render less pixels per frame, so you speed up your fps quite a bit more than any other method.