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I couldn’t find official dimensional accuracy specs for any formlabs machines except the 1, which lists 150um. Perhaps you’re talking about the 3, which has a specified minimum spot size of 85um according to this paper. Where did they claim micron dimensional accuracy?
There’s probably a bunch of reasons for the multi wing design, but the big one is going to be improving lift/carrying capacity without increasing the width.
The most efficient wings for low speeds are glider wings: as long and thin as possible. That makes them inconvenient to pack and folding joints are weak points. The second wing adds lift, but also problems: it’s less efficient than a single wing of the combined length would be and the front wing makes the rear wing less efficient. The winglet improves the situation somewhat. Facing downward also improves maneuverability.