This is some scary shit. The levers don't displace the fluid needed to actuate the brakes properly, or the design doesn't allow for pads to advance as they wear properly. I would heavily bet on the latter, but there could be many causes. One is simply that the bladder isn't flexible enough and requires more vacuum to maintain its displaced state than the the system can hold (e.g., the system is not well sealed compared to the bladder's static properties). In practice, all of these systems require some air to be present in the system, as otherwise, a perfect bladder material would be needed; however, you also don't want too much air. It's also possible that the system is consistently hard to bleed, but that seems unlikely. Further, the videos showing that the mechanics can easily replicate this in the stand suggest it's a design issue. This would be a recall if it were to happen in the US or EU.
Perhaps Magene recognizes that they have some product design issues to address, which is why they decided to focus on China before entering those markets where regulators and consumers have historically been less forgiving. I hope the chinese cyclists continue to hold them accountable and that they roll out fixes, etc.
Some of this story reminds me of a problem I had with my Wheeltop EDS TX brake levers that for some unknown reason would lock up solid at the levers. After this happened 3 times, and I came very very close to crashing on a descent, I replaced them. Wheeltop had no interest in helping me to discover why this was happening. (I believe that the pistons in the lever housing jam somehow. The levers are still sitting in a parts bin.
Your type of failure, though no less scary, is more common. While it is also possible that the levers are physically jamming, I expect someone else to have observed this issue and replicated it, especially since you experienced the problem with both levers. The lack of return is likely due to the design of the wheel top system. Still, I wouldn't immediately consider this a design issue that needs a recall, as it could be an installation issue, bleeding, or even a case of using the wrong hydraulic fluid--conditions potentially which make the wheeltop design a poor one to avoid buying, but not a dangerous one.
I guess what I am saying is that your wheeltop issue was bad, but this is next-level bad.