Although I find the thought experiments about this question relatively unimportant, a deeper look into the mythology says a lot about how Wing Tsun/Wing Chun people use convenient logic to push a narrative. Often it seems things that either has meaningless or tertiary importance get built up to undeserved proportions.
The missing right Slant Kick is one of a few unnecessarily mystified points in the system. It is one of many examples of how confirmation or outcome bias breeds systematic “genius” justifications where in fact, none may exist.
I am a firm believer in the principle of Occam’s Razor. This principle is based on an idea that considers competing propositions one should go to the one, which has the least amount of assumptions. This is in direct contrast to how most Wing Chun “research” is conducted in which stories and hearsay are assumed as true so that a certain lineage’s marketing can conveniently support these assumptions. These forms of revealed history often coincidentally bolster the storyteller’s credentials or lineage. Curious how that works, right? But I digress.
It is true that some of Grandmaster Ip Man’s followers and grand students have modified their Chum Kiu to include the Slant Kick (or their version of the last kick) on both sides. This would be their modification, and as evidenced by the Chum Kiu forms of Ip Man students like Wong Shun Leung, Tsu