My understanding is that the 32-bit DAC just allows for additional headroom. Larger digital pipeline, so to speak. So, for example, you could do volume control digitally without losing anything form a 24bit recording. But my understanding is also that this is largely theoretical because there's nothing out there right now to really take advantage of it. Just like the 4k
passthrough... Also, keep in mind that "my understanding" isn't really any understanding at all. I'm not a sound engineer, but I can read...I feel like I should add that I stayed at a Holiday Inn Express last night.
TL;DR: It has no practical use right now for 99.9999999999% of the population, but as the saying goes in the audio (and PC, for that matter) world, there is no such thing as too much headroom.