I think it's also important to bear very much in mind the exposure some of the early TKD pioneers had to Chinese styles, particularly those in the northern part of the country neighboring Korea. Long Fist Changquan, for example, which was known to at least the Korean military for several hundred years (it appears to be the core technique set outlined in the
Muye Dobo Tong Ji's single chapter on unarmed combat) has been
described as follows:
The Long Fist style is considered to contain a good balance of hand and foot techniques, but in particular it is renowned for its impressive acrobatic kicks. Of contemporary wǔshĂą events, Long Fist techniques are most popular and memorable with its whirling, running, leaping, and acrobatics. Chanquan moves are difficult to perform, requiring great flexibility and athleticism comparable to gymnasts.
Long FistÂ’s arsenal of kicks covers everything from a basic front toe-kick to a jumping back-kick, from a low sweep to a tornado-kick. Specifically, typical moves in modern Changquan include: xuanfengjiao (旋风脚; "whirlwind kick"), xuanzi (旋子; "butterfly jump"), cekongfan (侧空翻; "side somersault"), and tengkongfeijiao (腾空飞脚; "flying jump kick").
Something that's important to bear in mind when investigating historical origins is just how far and wide objects and ideas can diffuse. My favorite example is Ireland in the Dark Ages—nominally one of the most isolated periods in European history, when roads were barely maintained, economies were almost purely local, infrastructure was a mess, and feudalism was just beginning to get started. Near-chaos. But analysis of the blue dyes in the reknowned early-9th c.
Book of Kells, maybe the greatest illuminated mansuscript of all time, created on the tiny little rock/island of Iona, reveals that these dyes were made from ground lapis lazuli, which was available at that time
only from Persia. Thousands and thousands of miles of dangerous passage were somehow successfully negotiated—on a regular basis, apparently—to supply the scriptorium in maybe the westernmost place in Europe with necessary supplies. And there are many similar well-documented cases, showing how much contact even distant human groups maintain with each other, even during the worst of times.
Given this pattern (the Silk Route is another brilliant illustration of the same thing), it's very difficult to completely isolate and localize the source of particular cultural elements—including literature, music, graphic arts, building styles and methods... and fighting techniques. It's a pretty safe bet that stuff in all of these categories circulated widely, and given the long-documented impact of imperial Chinese culture on its neighbors, it's not surprising that so many of them have a good deal in common with the expanding Han empire, even if they inevitably supply their own twist to it...