REVelation… Random ?

I have been a happy Nuendo / Cubase user since the beginning of Cubase – back in the ‘90s.
Today an unusual situation came up. I called up a mix I had been working on and listened for a bit and when I listened to the same section again, it seemed to sound different – even though I didn’t change anything!
As a test, I rendered the mix and checked “Import Into Project” in the Export Audio Mixdown window.
Now usually when you do this and you reverse the phase of the 2-mix, you will hear silence. But, I didn’t! I heard reverb!

I repeated the same test and this time muted the return on one of my reverbs: Steinberg REVelation. And guess what? - Complete silence when I reverse the phase of that 2-mix!

That tells me that REVelation is not producing the same reverb every time you send the same thing to it. Is this what I should expect, because it is an “Algorithmic Reverb” ?

Is modulation on?
I don’t know (and not in a position to test right now) if there are any other random elements in the algo but I would expect modulation to not null.