Do you know all that or is it your educated guess (no offense intended, appreciate the input). For the longest time I have wondered how this was recorded and mastered (endlessly after the fact it seems - and I prefer the CD rip I have over the HDflac download).
Educated guess. Monitored on headphones [Drop 6XX]. A two-microphone recording would have different piano sound right and left. This is panned mostly to the right, there's no stereo spread of the piano. I've made two-microphone recordings of pianos solo and with other instruments. Two-microphone stereo, like ORTF, would have some piano in both channels and there would be a tonal difference between the two channels. But this pretty much sounds like a mono source panned to a position slightly less than hard right in the stereo image. And, as I said before, there's very little audience sound in the mix.
I've heard plenty of live Jazz on record, here's a great example, Duke Ellington, soon after the famous Newport performance. This sounds like two-microphone stereo, there's much more audience noise even though group playing is much bigger and louder than the piano trio recording. While the piano is positioned hard left, you can hear its sound splash off the walls of the room, with a different reflected sound on one side than the other. The effect is even more pronounced with the drum kit, which seems to get bigger as it gets louder. Should note there's an earlier volume in this series, I like the sound quality on that better, but the YouTube needledrop of that disc sounds like a mono fold-down, of a stereo LP. Look for "Duke Ellington All Star Road Band, Volume 1", I've got the CD. This track is from Volume 2: