Steps to Reproduce

1. Create a world with the redstone experiment enabled
2. Build a setup according to this screenshot:

3. Flick the lever a bunch of times and observe the result
4. Replace the repeaters with redstone dust
5. Flick the lever again multiple times

Expected

In both cases, the random left/right preference is determined once and either the left piston extends for all of the rotations or the right piston, but never a left piston in one of the branches and a right piston in another at the same time.

Observed

With repeaters in place, for some of these the left piston will extend and for some of them the right piston will extend, while with dust it's always consistent for all branches.