I also asked about the mixer presets several times and never got an answer. Don't understand. What's the problem in answering a simple question? I find it very difficult to understand what's going with the presets, they are very different to other libraries on the market.
For me this delay is more like a pre-delay of a reverb. They treat the ambient mics like a reverb and focus on the close mics. I spent a long time with the delay settings and still have no clue what setting should be right. I'm not that happy with the mixer presets.
I also don't know if the close mics have a delay built in or not. If not: the close mics should have a delay. And even close and mids should have slightly different settings, because they are not at the same position. I experimented with this a lot and found out that this also reduces the phasing issue with the vibrato crossfades in the strings (which is annoying and doesn't get fixed, I mean this a no-go considering the price tag, no other library has such severe phasing issues).
In general they use three numbers: 15ms, 21ms, 42ms. I first thought that these are the distances of the close microphones, but this would mean only three positions from the decca tree. Every close mic needs a number on its own. And only VSL can measure and tell us these numbers.
Would be really nice if someone from VSL could finally tell us a bit about this. In my opinion there is a huge difference in sound when using various delay settings. I know the saying is "If it sounds good, it sounds good", but it does not sound good, for my part.