The use of ‘irregulars’ to do the dirty work of looting and intimidation gives some political cover to the Russian regular army. “Hey look, it wasn’t us!”
As if any of the human rights NGO’s will have much to say about the whole thing, except to point fingers at both sides.
You can find similar behavior between Kansas and Missouri before and during the US Civil War.

And yes, it is by design. And I would not be surprised (although it could never be proven) that there were Spetznaz officers sprinkled among the irregulars to make sure that they don’t tire of the looting and random killing too soon, before the political objective is reached. That is terrorizing the Georgian people sufficiently so that they ‘vote’ the correct way next time, and choose the Russian political puppets selected to keep Georgia emasculated, and in the Russian orbit for the forseeable future.
“More of this, or do you like your worthless Western friends”

And the Cuban Missile Crisis was designed to be a trade-off; we would get the Russians to pull out of Cuba (eventually), and they would get West Berlin. We just got lucky and caught them before they were ready, which cost Kruschev his job two years later. The Politburo hated surprises and public embarrassments.