Why is the layout different on mobile?

[nwnuyhs (Yang Hongsheng)]

This is F12 mobile layout:

This is in mobile layout,can anyone tell me why the two layouts are not same?

[Jagster (Jakke Flemming)]

I can’t tell why but the first one is desktop layout.

[Heliosurge (Dan DeMontmorency)]

Yes what Jakke said.

In your top pic open side bar near bottom of side bar there is a toggle if you want to see mobile view.

[merefield (Robert)]

You can make desktop more consistent with mobile by using this setting: