One way to look at it is that mitered binding corners are so small (and somewhat crinkled after washing), the chances of a wonky miter standing out at the end are very small, compared to the likely heroics required for butted binding to not attract the eye.
I’d keep looking until you can find a video or article you understand. I am very spatially challenged and always have to review the directions before doing it. Some online instructions make things as hard as possible, IMO, to make the presenter look more expert.
Also, no one intentionally tries to have a seam in the binding land on a corner, yet it sounds like you’d be dealing with that on all 4 corners if you butt them.
The rounded corner idea is a winner, too. Just know that you may have to insert a line of basting stitches near the binding fold to ease the fullness in at the corner. I’m doing one now, with a binding and ruffle. Can send you a photo if you need it.
hugs, charlotte