Sorry, I'm confusing myself again.
I came across a document about PWM filters: http://www.proaxis.com/~wagnerj/PWMfil/PWM%20Filters.pdf and on page 12 there's a graph of what happens to the filter output when there is a narrow pulse. I was concerned that because a single pulse of 10-bit PWM is narrower than that of 8-bit PWM, and with a high frequency, that the filter would not work correctly. But having thought about it some more, I think it will still work.