Interesting stuff.
Goes against what I figured regarding instrument tracks, vs. multi out from rack.
I’ve usually used tracks for single channel VSTi and racks for multi-channel.
For me, I prefer being able to save up to 16 slots as a multi under one preset, and further be able to gang control those if needed.
That has generally outweighed any CPU/core benefit, if there were indeed one from manually delegating cores per VSTi.