First, you don't really need to use a custom command here: the Set Dimmers and Bulbs > Set dimmer level action in Rule Machine (or Button Controller) already does this. That being said, as long as you chose the right parameter types, there's no reason either way shouldn't work, so I don't think this is actually the problem. But it's easier. 
The second thing you could try: do you have a reason to prefer Inovelli's drivers? (I'm not saying there aren't any; they support all five taps and not just two, and they have a couple features that let you more easily set notifications than the setIndicator() command does in Hubitat.) If not--or even if you just wanted to test this--you could see if the setLevel() command acts differently on Hubitat with their own driver. If so, that gives me hope that Inovelli's could be modified to respect the rate, which it's possible theirs doesn't in some cases (I have not looked at their code, so I have no guesses). Changing to Hubitat's should not overwrite any parameters except for preferences you set in the driver, which applies equally to both drivers.
You also don't really need to use the setConfigParameter() command manually, as Inovelli's driver exposes all of them in some way, so changing it there should do the same. But, again, as long as they were set correctly (and not overwritten if you re-saved device preferences), you should still be good. If you want to for-sure compare the parameters to the values in the manual, you could also use the Basic Z-Wave Tool (switch to it, then switch back before trying any "real" device commands).
