After working on and rebuilding an XDA-2 DAC and looking at the XDA-1, my only answer would be "maybe?". I see two 2134 op amps after the fully differential AD1955 DAC chip. This suggests that the opa2134 op amps are working in fully balanced differential mode for the I/V section. After that, it goes straight to the discrete analog output stage. It is difficult to tell if this discrete analog stage is fully differential/balanced, but I would only assume so.
This is different than the XDA-2 dac, which has the same two opa2134 I/V op amps, but then goes through another single opa2134 op amp which acts as a low-pass filter and downgrades this to "single-ended". Then the XLR outputs have their own set of opa2134 which convert the single-ended analog back to differential. The XDA-2 is not "fully differential" from end-to-end, but the XDA-1 DAC might be.
This is different than the XDA-2 dac, which has the same two opa2134 I/V op amps, but then goes through another single opa2134 op amp which acts as a low-pass filter and downgrades this to "single-ended". Then the XLR outputs have their own set of opa2134 which convert the single-ended analog back to differential. The XDA-2 is not "fully differential" from end-to-end, but the XDA-1 DAC might be.