We can only assume stuff on the Hegel balanced input. It’s entirely possible that it is using all pins on the XLR. This means that it will use both the positive and negative polarity signals on the XLR, as shown in this op amp example:
However, I highly doubt that the signal is balanced after this. The op amp will convert the balanced (+/-) signal to a single-ended "unbalanced" signal internally. The amplifier part of the Hegel is not going to be fully balanced/differential. It’s difficult to see, but it appears that there are 4 transistors mounted to the amp heatsink. This means it’s only single-ended. The amp will use 2 transistors per channel (one transistor for positive side of waveforms and a second transistor for the negative parts of the waveforms. There aren't that many amps that are truly balanced internally. They are usually monoblocks, but ATI and Theta have models that use balanced amp cards.
http://2.bp.blogspot.com/-d9V_PoFrbx4/UzHRUZXW_RI/AAAAAAAAXLw/wzgZdKol-Ok/s1600/HegelH80-07.jpg
That being said, I have always had superior results using balanced connections, even though the source/preamp device is not truly balanced.