I also note the mixture control is not tested on the runup. I always lean with carb heat on at runup RPM. You should see a rise as the overrich mixture caused by the carb heat is leaned back to best power and then a drop as the mixture goes too lean when you continue to slowly pull the mixture knob out. A very usefull check that the carb is working correctly
Seems strange to me, I always set the best power mixture before I do my power checks, at higher altitudes you have to lean before you start taxying otherwise your engine may cut. Checklist actions may need to bend depending on what environment you are flying in, especially relating to the setting of the mixture, just following checklists parrot fashion is not a very good thing to do.