I hate to interrupt, but there is a fallacy that needs addressed here. Yes it is true that the LDBK can be proven to exist prior to Yip Man. There are a couple of points to address here though.
1. The pole seen in YMVT, as verified by Lam Guei Chung's HSHK version, is also present in YKSWC & Kulo.
2. Since the existence of the pole is applicable as being pre-Yip Man, so must to be, the empty hand sets SNT, CK & BJ as these sets are also passed on by YKSWC & other Leung Jan lineages, the same as YMVT. Theory, principles, methodology etc. of the forms and pole of that time cannot be definitively proven, only outward appearance.
3. Even though the appearance of the empty hand sets differ slightly, it doesn't mean they didn't exist prior to the pole. We can deduce that at minimum they existed at the same time.
4. Yip Man's version of the empty hand forms didn't exist prior to YMVT, because YMVT didn't appear prior to Yip Man.
5. The significance of the YMVT empty hand forms being based on the pole is only applicable to YMVT and could only have occurred prior to Yip Man, with Yip Man or after Yip Man. But this does not at any point eliminate the existence of SNT, CK or BJ until the emergence of the LDBK. Because if we take the previous points into consideration, we see that the empty hand sets, like the pole were passed on independent of Yip Man's lineage.
6. This leaves the conclusion that any correlation to pole with empty hand occurred only within the Yip Man line and since the existence of SNT, CK & BJ can be verified prior to YMVT, that the merging of the theory could only have occurred in one of the following ways:
A. Leung Bik/Fung Wah taught it to Yip Man. Since no other students of Chan Wah Shun pass this on, he can be ruled out.
B. Yip Man re-engineered the hands to align with the pole and passed it on to a select few.
C. Wong Shun Leung formulated this methodology and passed it on.
There are no other possible solutions based on the available evidence that would support a plausible explanation.