Just a personal perspective in this matter, which is obviously very distressing for the couple whose light is being blocked.
I am not suggesting our experience is relevant to your problem, but it may be food for thought.
We have a very nice garden that includes a small orchard, several lawned areas, a chicken run and a family-sized potager.
It is very secluded in all sides by hedges, trees and shrubs. My wife loves to sunbathe, often with some of her clothes loosened, but never nude. But she hates being ogled, or even seen when lying on a recliner. She feels very vulnerable when in repose and with eyes closed.
Many women feel the same. It is possible that one or both of your neighbours feel the same and, even though your windows are frosted, feel on edge at the presence of your window. It might seem unreasonable, but some people are very private, to the point if being prudish, and any risk of visual intrusion on their intimacy may be intolerable. But it’s hard to explain to others, because it may be taken wrong, as if they are being accused of voyeurism or worse.
It’s a question that might be resolved by sensitive discussion, perhaps between the women party to the problem. It seems to me that it is highly unlikely that the screens are intended to deprive you of light, it would be mindlessly petty. There is almost certainly a more human reason IMO. Just a suggestion!