Worth noting that the isolation for the USB 2.0 portion is actually the same for both.The 7055-C (3.0) has less noise than 7055-B (2.0). The manufacturer posted some measurements. I’ll find them later.
Their isolation rating is also different (1kV DC vs 5kV AC).
The difference is in how the USB 3.0 lanes are isolated, which you're not actually connecting when using a DAC.
But yeah the lower noise is the main reason.
Noise measurements:

EDIT: Sorry thought you were meaning 7055-C vs 7055-D. Yeah the B and C are indeed different in isolation, apologies
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