Originally, SegWit was conceptualized to include a single push where the first byte indicated the version and the subsequent bytes contained the program itself. This design allowed for the push to range between 2 and 41 bytes in total. However, the current implementation has diverged from this initial concept, separating the version and the program into distinct pushes. Consequently, the length of the program is now constrained to be between 2 and 40 bytes, excluding the possibility of a one-byte program.

This modification addresses a potential source of ambiguity inherent in the original design – specifically, the confusion surrounding the method of pushing a single byte onto the stack. The ambiguity arises from the various ways a one-byte value could be interpreted or represented within the script, such as using an opcode for the numeric value (e.g., OP_1) versus its hexadecimal representation (e.g., 0x01). By enforcing a minimum program length of two bytes, the revised SegWit structure effectively circumvents this issue, ensuring clearer and more consistent script execution. Further details on this topic can be explored through discussions and questions posted on platforms like Bitcoin Stack Exchange, where community members delve into the nuances of Bitcoin's technical framework. A specific question related to the comprehension of how a two-byte witness program could be logically implemented provides further insight into the reasoning behind these design choices, highlighting efforts to enhance clarity and prevent misinterpretation within Bitcoin's scripting language.