Miyke

I too am part of the idiot mouse radius religion. And spoiler alert because reality often ruins religion, it's actually real as confirmed by Jnash in his stream. Although it's Real for every single rarity not just runes and gold and Its a higher chance not a guarantee.

I have never confirmed the radius theory, I like to mess around with chat about it, but there is no evidence that this is actually a thing supported by the game's programming.