It seems to me they are using it, but as you mentioned navigation may not be the purpose. There may be none. It may just be that insects that do this congregate and reproduce thus it’s just a mate finding thing that’s evolved. Since insects often have short lives, I’d guess it also explains why they’re always doing it (they need to mate asap).
Might also explain why they don’t go directly to the light but eventually end up there circling it erratically, increased odds of bumping into a mate.
The paper mentions that the insects enter stall conditions, maybe due to the banked orientations, sometimes and then recover. This would explain erratic behaviour without any mate present.
Might also explain why they don’t go directly to the light but eventually end up there circling it erratically, increased odds of bumping into a mate.