The elbow height comes from old visdom when you need power like filing. Think of vice, clamp iron and start filing.
https://ergo-plus.com/fundamental-ergonomic-principles/There is a difference when arms are used to manipulate something on confortable height. Think of drawing board.
It is actually beneficial to have to move a little on not too essential controls (as long as you don't need to hunch over something dangerous or reach too far to trip) ocassionally. In modern offices peope have way more restricted mobility on "mouse hand" than non-rodent-hand.
Long winded story...where I am getting at?
When lifting: Hands should be in "Power zone" when reaching or lifting or using heavy controls. This is standing position. This ofcourse has a little consideration if the parts you machine are very light weigh and your milling machine has no 1930 lever operated clutch.
When working (sitting or standing): the hands should lie comfortably on the most used controls. And E-stop (button, stomp bar) should be easy to operate.
I see some people hunching over a small lathe like vultures over carcass, that can't be too comfortable. Clock makers lathe table is diferent than floor mounted affair.
Habits are hard to break...I mounted one lathe to "perfect" height. I made the table. 15 years later it is time to come clean and make a new table for it ....it is too low, I can comfortably hunch over it. The thing was - it was perfect height for my vision, now I need glasses (and often magnifying lense), I would like to have it "closer".
Pekka