Ha. I was reading a thread about this on FB the other day and I was sure it was relevant to something and couldn't place what until now
Obviously now, I can't find that discussion to refer back...
You're spot on, based on that other discussion. I'm sure the basis was that one of the tensioners is at zero and the other is at 12, or 24, until they have pressure and then they end up the same.
With oil pressure they must be the same since in the FL1 the solenoids are connected in parallel to a single output from the ECU, so they must both advance and retard together. Its only in the FL2 they are controlled separately.