I should probably clarify. In 3E, there was a whole subsystem of mechanics governings hirelings and cohorts.
I don't see anything of this here.
Obviously I realize the worth of having an official "yes, it's okay to allow NPCs as allies" statement from the designers.
But other than that, it seems there is no crunch needed to run an ally*. Almost all of the excerpted text could be categorized as DM advice, and probably should have been presented as freely running text, rather than the numbered list, which suggests a procedure you should follow and could benefit from.
*) I'm guessing the referred-but-not-shown guidelines for ally hit points and surges will recommend less hp but more surges (changing the ally from being a monster into a PC in this regard). However, I'm not so sure that actually is necessary. Having lots of HP but few surges does seem to be a neat simplification, and allows the PC Leader to focus on the player characters.