As far as I know, it was necessary in the past, way back when Slot 2 cards were used. You needed a way to boot into it. Slot 1 PassMe cards were used to execute a GBA ROM in DS Mode at boot time. Eventually, someone figured out how to use the exploit to boot to the same card as the card used in the exploit process. The first Slot 1 flashcard was made. Much later, the first non-autobooting card was made. These don't use that exploit. They use a different one to fake a valid header in order to seem like retail cards that can be started from the DS menu.
Tldr:
Old cards autoboot, new cards don't.