You can achieve a smooth feedrate with the proper hydraulic flow controls etc, the problem is, is if you have to alter the feedrate you would have to do that manually unless you went with a hydraulic servo valve and feedback scale or encoder,This works exactly like a servo motor and ball screw etc. but now you are really getting up there cost wise. Perhaps he is worried about the use of a stepper stalling & losing steps under high load.
Al
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.