Bit 2 indicating if the current gba is the parent or a child should be set accordingly before the first transfer.
mgba indicates every console to be a child if no transfer has happened yet
This is not in line with how real hardware behaves.
mgba version 0.10.1 as well as 0.11-7891-d08b307be (latest dev version from the website as of writing)
OS Windows 10 64 bit