I am designing my first PCB with an MCU and I see this section in the datasheet that brings up a loading capacitor used for pin parameter measurement.
I don't believe this is load capacitance for a resonator because that value you get from the resonator datasheet and the figure doesn't match the needed connections. From looking around it seems this is related to S parameters for high-speed PCB simulation and verification, but it's hard to tell for me. This is from STM32F446xC datasheet.