I'd guess that the main reason for this somewhat complex power section of this amp is to make it as lightweight as possible - since manufacturer's strategy is direct sales, it's pretty important to keep the weight as low as possible - amps need to live through shipping process. In the end, it's the cost - packing cost and shipping cost. But manufacturing cost as well, since quality transformers are expensive. But I'm not convinced if classic transformer of a decent capacity would not be a yet better choice when it comes to sound quality.
OTOH feedforward is a commendable approach IMO. One wonders why it's not used more widely in amp designs, especially taking into account that this design approacvh is like 35-40 years old, or even more? And speaking of the concept which seems not to be the most liked one - the time domain - feedforward is pretty much the most sound approach, as it follows the signal path in the time domain, unlike any feedback - and I'm somehow confidend that low distortion of this amp greatly depends on feedforward design.
As for the time domain, at least few of the local audio designers are confident of its importance. Also, the one I talk to often is pretty confident of using subjective listening tests in evaluating the sound quality, even if it's not DBT. However he's a trained pro - such are usually trained to use their ears professionally while their eyes are being open, you know