You are right, removing a random instance changes orders in both ISMC and HISMC. (Instances change color.) Additionally, if I am removing only the last instance in ISMC, order doesn’t change contrary to HISMC where it does.
However, adding an instance changes color/order only in HISMC.
Also, I have noticed that sometimes when updating Transform in HISMC, instances also swap colors/orders.
*Now in 4.19 Preview 2