The main seals are fine, but this model has a double seal on the caliper — one main fluid seal on the piston itself, then another square “wiper” seal inside on the caliper body near the edge that appears to be intended to keep brake dust, etc. out. It’s not designed to keep air in or out on the outer dust seal in the caliper — at least not that I can tell. I’m going to order a new set anyhow and that should take care of the issue.
I will say that the Swiss Hutless system is the best engineered system I’ve seen — remote reservoir built into the master cyl. that allows for recirculation of the fluid when the pads retract so that it’s always self-filling and stays “full”… It must work somewhat like a piston-port.