I'm not sure if randomness would be enough to do this, but if not, they could probably control things a little bit, at least for the Dove satellites (88 of them). Since the Dove satellites can point themselves to take pictures, my guess is that they can also choose to point themselves either perpendicular or parallel to the orbital direction. Since there's a little bit of atmosphere left up there, over time that should be enough to intentionally spread the satellites out.
This is just a guess, but I know similar techniques have been used in the past on satellites that were out of fuel - for example, Skylab.
https://support.planet.com/hc/en-us/articles/212641458-How-d...
This paper covers diff drag in more detail. https://arxiv.org/abs/1509.03270
A relit final stage can put satellites in significantly different orbits. Satellite thrusters can do a little but only small orbital changes. And just releasing over a period of time will result in each sat being released on the order of 1 m/s which is enough to keep them separated but in the same orbit.
Some rideshare launches have multiple burns of the upper stage to put payloads in different orbits. The PSLV can do that, though I don't know if this one will.