If I'm understanding you correctly, you're saying that while a perfect sinc interpolation reconstruction would allow you to capture up to 44.1/2 kHz, in practice since we're limited to FIR reconstruction filters we can't actually get that high? If so it seems like a fair point, although I'd imagine they'd be better than 6khz?
There's also the issue of the input signal not being band-limited which is necessarily true for real world signals given that you sample for a finite duration.
There's also the issue of the input signal not being band-limited which is necessarily true for real world signals given that you sample for a finite duration.