At the lowest level biology is physics. And physical systems are not approximate, they are exactly what they are, and a small round-off error can give a huge difference in the specific outcome, even if on a macroscopic level that outcome might be indistinguishable from the 'real' outcome.
So the real question then becomes does biology tolerate working on an approximation of the underlying physics and does that simulated biology still have the ability to exhibit intelligence. I think the first is a maybe, the second a yes but I couldn't give you any reasons why other than that it might be that our biology needs 'its' physics to operate and that probably anything Turing complete has the potential to exhibit intelligence, regardless of whether or not we find a way to achieve that.
So the real question then becomes does biology tolerate working on an approximation of the underlying physics and does that simulated biology still have the ability to exhibit intelligence. I think the first is a maybe, the second a yes but I couldn't give you any reasons why other than that it might be that our biology needs 'its' physics to operate and that probably anything Turing complete has the potential to exhibit intelligence, regardless of whether or not we find a way to achieve that.