Wait, so the pattern was created using some random RPU, with the x265.exe encoding BL/EL done separately? That seems odd when he could have simply created the pattern in Resolve, delivered it as 12-bit ProRes or JPEG 2000, and then used Dolby's own tools (the Dolby Encoding Engine) to generate a proper Profile 7 BL, EL, and RPU.
The task was to strictly output 2 bits of data to the EL layer. Therefore, a solution involving direct editing of only the EL layer was necessary, since it is impossible to control how the DEE encodes the data—or what it decides to classify as residual data.