I wonder if it was just meant to use the highest of each drone or those of the RCC and they worded it poorly.
However, the interpretation makes sense: If each drone shares it's autosoft, only one needs to get them from the RCC and everyone gets them.
Swarm fixes a lot of problems. Though doesn't that mean you could run 1-Drone Swarms, hypothetically? Or add a Noizquito to any legitimate combat drone for twice the benefit?
Each swarm acts as a single drone with multiple, separate
“bodies.” Its Pilot rating is equal to the highest Pilot
rating of its member drones, or the Device Rating of
the RCC, whichever is higher. The swarm uses the highest-
rated of each autosoft running on any drone or the
RCC, and the highest Sensor rating. It uses the lowest of
the drones’ Handling, Speed, and Acceleration ratings.
When performing actions, the swarm gets a dice pool
and limit bonus equal to one less than the number of
drones in the swarm. <emphasis mine
Theoretically- no...throwing the hard cover core book at you.
Bodies and drones, highlighted above, are both plural.
Let's not get into the definition of the noun 'swarm'.
Sadly, two is a swarm, so yes you could add 1 microdrone to a combat for the benefits of a swarm. But really-why?. The microdrones are cheap enough- add five to give the combat drone +5DP and Limit to it's actions. With a DR6 RCC you could run 3 of these swarms.