it's best if the sync adjustment does not change quickly.  I would like to change the adjustment on every call, but there were too many edge cases near the beat markers to make that calculation straightforward.  It's safe to use the previous sync adjustment because the value is quite stable, so it's not a big deal if we use the previous value.  The adjustment is not anywhere near low-latency precise -- it's a nudge, and the nudge from the previous loop is probably safe to do on the current loop.

You can try it yourself by playing two tracks, letting them get out of sync, then engaging master sync and quantize mode for both.  The tracks move nicely together.