I’ve looked over their materials. I understand the idea. It produces numbers that are pretty to look at, and fits well into a marketing message about being “mathematically lossless”. I don’t think it does harm.
The marketing message is black+white…mathematically lossy is “bad”, their product eradicates it. Previously digital volume control was problematic, now it is the equal of analog domain volume control thanks to this innovation. Plus, volume control in general prevents hearing loss and tinnitus 
.
Poking fun aside, I have some more technical thoughts.
One problem with their line of reasoning is that it assumes “mathematically lossy” processes like truncation are inherently problematic. We have many good reasons to alter audio signals irreversibly, and lots of mathematically lossy stuff happened in recording/mixing/mastering, and more happens in the DAC chip post volume control. This doesn’t mean that information loss is “good”, it just means that to discuss this topic honestly, you have to consider the magnitude of information loss, the places that it happens in the processing chain, the nature of the information loss at each point, and how it plays out end-to-end, from the recording studio all the way through to your ears.
These marketing materials focus on one attribute of the process–mathematical reversibility, treat it as a black+white benefit, and then focus only on one step in the chain in isolation, and then from this narrow vantage, make an argument that their approach addresses the past problems of digital volume control because it doesn’t leave you with any non-zero bits to truncate away.
If I look at floating point volume adjustments through the same narrow lens as these marketing materials, floating point comes out even better: floating point multiplication within the ranges used in audio processing is mathematically lossless without requiring imprecise volume adjustments. No special techniques required.
(Of course they aren’t arguing against floating point processing or even considering it in their arguments–they are implicitly comparing to an integer-math volume control, because they are more common in hardware products).
I don’t use FLACs because they are “lossless”. I use FLACs because after ripping to FLAC, I have captured 100% of the information on the CD so I can stick it in a box in the attic and never have to worry about ripping it again. I know that the original mastering process was not lossless anyways, so I am under no illusions and I happily accept that even the best DACs perform mathematically lossy operations that lose significantly more information than the truncations discussed by Leedh because it is just part of how audio is reproduced. It is not so black and white.
One final point–the main reason why digital volume control can be a disadvantage is not that it sometimes involves mathematically lossy processes. It is because of where it sits in the processing chain. It necessarily consumes some of the overall signal-to-noise ratio of the end-to-end system. The analog components are a much stricter bottleneck for SNR, and a quieter digital signal put through the same analog stuff operating at the same amplification level is going to to have a smaller effective dynamic range, whereas an analog amplifier with a volume adjustment can be designed to have roughly the same SNR across a range of volume levels.
Those effects aren’t in “quibbling about bits and truncation” territory anymore. If you had 100dB of usable SNR to start with, and you chop off 20dB of it digitally with any technique, the quality difference will be in “audible to a layman” territory regardless of how it’s done.
In most systems there will be some space for digital adjustments without doing meaningful damage, but the core implication of these marketing materials is that the longstanding “problem” with digital volume controls is addressed by this innovation, and I’m not sure how something like this could go that far. I can say that I won’t be pursuing it for my own listening, based on their published information.