What part of the wing is creating lift, and forward velocity at >40 degrees AOA? The roots probably stall below 20 Degrees, and the wing is fully stalled at a few degrees more, the tips stalling last in normal wing design. You should get a good pitch down moment while the root is stalled, and still have roll authority. Beyond that, the machine is no longer planing through the air.
Note that skydivers, before they open their parachutes, have a glide ratio at a very high angle of attack, just not a very good one. With a fabric "wing," the glide ratio improves. Click
for an example.
Similarly, the wing is still providing "lift" beyond the stalling angle of attack, just less and less of what it was before, and more and more drag. The airplane should pitch down at stall because the center of gravity is ahead of the center of lift but in this case, the center of gravity may not have been been very far ahead of the center of lift and you've obviously got engine thrust, an almost fully nose-up trimmed horizontal stabilizer (which is probably sized to keep the cg range as wide as possible), and nose-up elevator creating enough nose-up pitching moment to offset any nose-down moment. I am surprised that there was still enough roll control authority at that angle of attack to keep the wings more or less level.