deSitter;
That, and its size, would seem to indicate that the structure is part of the elevator.
Except the attach points on the elevator are more evenly-spaced, while the aileron attach points are close together.
I can't judge the size because I don't know how large the elevator is compared to the aileron, at that point in either structure. An oxygen bottle is about a meter long and that's about how wide the flight control we're examining is.
I don't think it's flap, (because of the two attach points) but further photos are needed before we can determine origin.
I think it is important (especially with so little real evidence) because one outcome is "wing" and the other is "tail feathers".
regards,
PJ2