Compression setting on rear shock not doing anything

[BMG]

I recently bought a 2018 XC300. I've been playing with the rear suspension settings. Changing the rebound makes a noticeable difference to the rebound speed but the high and low speed compression feels like it doesnt change at all not matter how many clicks or turns I make on the adjustment.

I've been away from dirt bikes for 15 years and been mountain biking instead and on my MTB rear shock the H/L compression does make a noticeable difference, so I assumed it would be the same on my XC.

Should I feel big difference between open/closed when testing on a stationary bike? I was expecting that I should?

Cheers