Peacock stirrups are elastic band stirrups right?
I use those now because I'm a minor. It's frowned upon for anyone over 18 to use them, but my saddle came with them so I didn't care to change.
I've heard jointed stirrups can prevent you from sinking your heel down without bracing. I also imagine that they may not work that great unless you're at a precise angle.
I don't see how the ones you posted specifically could interfere with riding as long as you have some kind of pressure on your stirrup. I played with a pair at the store- they really don't unhinge unless you PUSH them with a good bit of force behind it. I plan to get this kind of stirrup once I'm 18.
"The wise man thinks he knows nothing.
The fool thinks he knows everything."