X axis is in MHz, it is write but maybe to small.
Yes, you have right it is in a skip mode because the load is large, it should sink 10uA with a peak 100mA when works but for very short time < 1ms. Oscilloscope has 1Mohm of input impedance. By the way, the output waveform is a sawtooth with superimposed high frequency ripple, i think the peak at 2MHz. The filter have to attenuate that ripple because the load is pratically ideal.
I try to reduce the probe ground wire lenght put it around the probe. The same peak are measurable on the air with the probe like an antenna but if i connect it to circuit peaks increase of 20/40db.
I don't know why the software use dbuV.