Good point. They won’t be comparable because they’re different voltages, so the regulator will behave differently even with the same firmware settings.
Your results demonstrated how much it can change from one ramp level to another though, even on the same light with the same battery.
Most regulators work by quickly setting an output level, then reading the result, then setting a new output level, then reading the result, and so on… so they naturally tend to oscillate. Most have configurable settings to controll the oscillation speed, because faster oscillations look better but use more power for the control chip, while slower oscillations are more likely to be visible but allow the control chip to use less power.
Additionally, the regulator has only limited resolution for the steps it can set the output to. So it’s unlikely it will be able to hit the exact level requested. It just tries to get as close as possible by oscillating between nearby levels.