The Prophet Rev2 has DCOs - Digital Controlled Oscs, while the PB has VCOs - Voltage Controlled once.
I might not be the perfect person to talk to, but slight differences of the 6 voices of the PB are possible. I encountered it too - slight swings of sound without LFOs in action, but I put it to the analogue voice modelling - and it puts to my taste a little life into it. I have a few digital synth too, where I need to synthesise in different ways the slight mistune...
If you mix VCO1 > VCO2 it might increase it even more.
- True, some presets are getting weaker depending on Resonance, Filter, Env Amt, or else. Keep in mind to use the individual preset output gain (Settings > Out Section > Preset Volume) to level it to other presets.
- Nevertheless: "sweep from low to hi" is not what I hear - rather, as mentioned a slight swing - like a soft LFO.
But maybe somebody else has a better explanation or different experience.