I agree with you about 90%, since we are still learning new things about AAS discovered over 50 years ago, there certainly is lot more to learn about Ostarine and SARMs in general.
However, Anadrol is not a Progestin, and I've never seen any claims that Ostarine would interfere with Progesterone receptor, since it's a SARM and specificly targets Androgen receptors, I would consider it nearly impossible.
I've red many different theories based on many different studies, about how and why Adrol causes Estrogenic side effects without being able to actually convert to Estrogens. In many cases it's been said to raise Prolactin or being a Progestin as you suggested, but personally what I've found to be most accurate, and what I base my arguments about it is very well stated in this text (I belive the author is Anthony Roberts):
"Since Anadrol 50 is derived from DHT, it cant actually convert to estrogen (via the aromatase enzyme), and its not a progestin or a compound with progestenic activity so the estrogenic (?) side effects produced by it are of a very mysterious nature. It has been speculated that perhaps it can stimulate the estrogen receptor without actually being converted to estrogen and that's about as plausible an explanation as Ive heard. However, things really get strange, when Oxymetholone has been used in studies to alter the female reproductive/menstrual cycle; in those cases, it has lowered plasma progesterone levels! (7)"
Anyway, Anadrol a topic for a different thread, and I'm not trying to start an argument with you about it, just stating my own opion own the subject...