So Manga Haruka being some type of genderfluid/non-binary wasn’t actually planned but was just Naoko trying to scrap/salvage her idea for a male Haruka?
I don't know whether those rumors were true or not but then you have to wonder why Uranus has the Tuxedo Kamen mask and cape...
Ouranos in mythology is the primordial God of heavens and is the father to the Titans.
Considering Mamoru represents the Earth despite being male, it's not out of the realm of possibility to think Uranus may have been envisioned to be originally male.
If anything, male or female, the original plot was for a love triangle between Usagi, Mamoru and Haruka.
As for Haruka being genderfluid, I always took Michiru's words as Haruka being physically and mentally female but has the physcial prowess and endurance the same as a full-fledged male (even possibly surpassing males in terms of strength) and hence possesses the strengths of both genders.
Unlike Makoto who has more of a magical, herculean physical strength to her.
As for the wedding rings, the thing is despite Haruka and Michiru being a couple in Dream, Haruka still longs for Usagi - crying at the thought of her and longing for her smile...
Haruka's speech during the Outer's reveal trailer -
'Our Samsara (cycle of life and death), be it our despair or hope, or even dreams rest by your side you who shines of a blinding light. Yes, you Princess' (barf)
The 'wedding rings' were even revealed to be a testament to their promise to raise Hotaru rather than true rings...
In Stars, Haruka is coupled with Michiru and is even forgotten in favor of Seiya - the new girl in love with Usagi = rinse and repeat...