That sounds largely bogus to me. Both 32-bit and 64-bit applications can use the exact same precision in processing, a 32-bit application would just be slower at it, but achieve the same perfectly accurate result.
Since he is citing 23-bits of accuracy, he is most likely talking about floating point, where "single precision" floating point (which in total is 32 bits) has 23 bits of precision for the fraction, and 8 bits for the exponent (and one sign bit) - while a double precision floating point value (64 bits) would have 52-bit of precision for the fraction, plus 11 for the exponent. Media Center uses double precision floating points all the way through in its DSP engine, both in 32-bit and 64-bit builds.
If anything, he might have been talking about getting DAWs to use double precision internally, but not about the architecture it is built with - because that wouldn't make sense. Certainly Media Center behaves identical in both.