Assuming it's a sigma-delta ADC, the input filter isn't very important. It samples at several MHz, and on-chip digital resampling produces the desired output rate with proper suppression of aliases. Regardless, the ADC clearly (from the 192 kHz sweep) has reasonable attenuation of input frequencies above 22 kHz. The behaviour seen can never occur in a linear system operating at 44.1 kHz sample rate. Therefore, something else had to be going on, and we found it: the repeated samples.