No feedback, no bias compensation, output driver uses an LED instead of diodes to match and track the output transistors and provide stable class AB operation, etc. Fortunately the mistake highlighted by Amir means the outputs will never be applied to the headphones. I see why it's a coaster.
BTW, the BoM says it is a 24-V relay, not sure where they mean to connect it, unless the driving transistor drops enough to hook to 30 V or the relay will pull in with 15 V.
But, they did not lie -- it is not what most would consider high-performance and they are up-front about that.