Nah opamps can be biased to work in Class A through their implementation, Hum seems to be using 3 opamp's with 6 discrete component's to create class A output, opamps are no different to a discrete design on a circuitry schematic level, opamps are just a circuit network that has been shrunk down and printed on a chip, so opamps can do nearly anything you could achieve in a discrete circuit, only opamps save space and cost (obviously a fully discrete design would be better) but opamps are the most viable solution in a dap, and opamps are still used in 2k desktop gear, so you can imagine that their performance is plenty good.
There are other dap's that use some form of class A output, like QA360 uses a opamp with 6 discrete transistor's for class A output, and Pono uses a opamp with a discrete diamond buffer output which is similar to class A. Pono ftw.