red
Buck conversion and tracking are separate but tied together functions
Cheap MPPT controllers might simply have a manual user adjustment for setting tracking, while high end units have a CPU dedicated for the job of tracking sweeping etc..... Yes buck conversion can and does happen without tracking changing.
BLF
What is this mystical MPPT function you are going on about?
Remember the PWM function (which is an integrated part of both PWM and MPPT controllers) is for battery charging not DC to DC conversion