Focus Peaking outdoors
I decided it was due to using F11. So I set the lens to F4 and it showed the same
The lens only stops down when you take the photo. During preview it's always wide open, UNLESS you press the DOF preview button.
So if you want to check DOF (with ot without peaking) at apertures other than the lens' max, don't forget to press the button.
Everything was shown in focus probably because you were at a wide angle on your lens. It can be good to adjust focus peaking sensitivity of you think it highlights too much.
Usually if you turn the focus ring you'll see that there will be more peaks somewhere, this is what is "the most in focus", but the rest is still sharp enough.