We examine the WBF Systems policy in this video.
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The policy directs us to term the Standard American 1♣️ opening as a Natural opening. The policy further stipulates that if an overcall over a natural opening does not show a known 4 or more carder suit, that overcall would be classified as a brown sticker convention. There are significant restrictions on the pairs who play brown sticker conventions.
Interestingly, the policy does not place such onerous restrictions on the overcaller if the opening is 1Nt. That has led to a plethora of methods that are available to defend against 1Nt opening. So many methods that a full wikipedia page is devoted to those methods. There is no such wikipedia page for defences against the standard 1♣️ opening. There simply aren't any uncommon methods. I doubt if people have given a thought to that possibility.