M951/M594 on CAN/2nd Gcode Stream 3.5.X?

[Finchers62]

The list of CAN Board Limitations does not list M951/M594, but it has been stated in past posts that it does not function with CAN expansions boards. I was wondering if the height following functionality is even feasible with the CAN expansion architecture? Would the sensor and control loop have to be on the expansion board for the Z-axis to not mess up move timing?

On the same topic, since the M951/M954 functionality uses the second gcode stream (from my understanding), Is there still a chance that this second gcode stream functionality will make its way into 3.5.X?

Thanks for any input!