It'll take the same path IF the filter cuts off completely at or below the Nyquist frequency. If it doesn't.. it won't. You are ignoring this important point. The only signal possible at 20Khz is a sine wave.. yes, because any other shape would by definition contain components above 20K. Hence the need for an absolutely strict filter of frequencies above 20K.. or more specifically, one that cuts off as completely as possible at or below Nyquist which would be 22.05K.
Look, start with the assumption that I actually know what I'm talking about.. then read what I said again.
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