PV panels are illuminated level based current sources. PWM SCC's are just 'ON-OFF' connection between PV and battery.
They control battery charge voltage by chopping on and off. When battery needs charging, the switch is almost continuously 'ON' so panel voltage will drop to battery voltage with the PV's illumination generated current going to battery.
You only need a PV panel voltage a few volts greater than battery voltage. You can put a much greater panel voltage on PWM controller but will lose potential PV power when the loaded panel voltage drops to battery voltage. This is where the MPPT controller DC to DC converter benefits the delivered PV power.
MPPT controllers need more panel overhead voltage above battery for DC to DC converter stable operation and the MPPT search process needs a high enough panel voltage above battery voltage to allow the MPPT controller to detect where the MPPT point is by varying load on panel and detecting the peak in output.
Most MPPT controllers will drop to direct ON-OFF PWM mode if they do not detect a definitive peaking as they do their MPPT scan.