Sometimes I think Haruka enjoys the confusion. She originally appears along with Sailor Neptune wearing a cloak and mask akin to Tuxedo Mask, leading the inner soldiers to believe that there's only one new soldier and one new Tuxedo Mask. I believe her reason for dressing this way and especially her choice of wearing the male version of the Infinity Academy actually IS to mislead others as a form of cover for her and Neptune. While the enemy may be looking for two sailor soldiers, they would never look at Michiru and Haruka as suspects if they believe Haruka is male. Haruka never wears a male uniform again after leaving Infinity Academy and dresses decidedly more feminine afterwards, though people still confuse her for being a man time to time.
Michiru's comment about Haruka possessing male and female strengths is sometimes misunderstood or mistranslated as her being both male and female. This refers to Haruka's personality alone; possessing strengths of both genders allows her to have an advantage that other soldiers do not possess, one of her special powers as an outer soldier.
As Takeuchi Naoko stated several times, the sailor soldiers are all female. This means that Haruka was never a male in her past life, nor does she start out as a man and change into a woman. In the 90's, a group called Save Our Sailors (S.O.S) published a fictitious story about Haruka and Michiru's past lives in the Silver Millenium. The story stated that Haruka was really "Prince Uranus" and he was in love with Princess Neptune. His sister, Sailor Uranus, perished in battle and passed her sailor soldier powers onto the Prince before she died. The story then claims that since sailor soldiers can only be female, Prince Uranus was reincarnated into a female to take the place of his sister, but still harbours his romantic feelings towards Neptune and continues to pursue his relationship with her.
This story is total bullshit. I'm not sure why the authors of S.O.S decided to publish such a bigoted article, but it's shown in the manga itself that Haruka was both the princess and the sailor soldier of Uranus in her past life. There is not even any mention of whether or not she and Princess Neptune had a relationship in the past, as they were both forced to spend eternity alone, guarding the solar system from outside forces. To me, the "Prince Uranus" story is an excuse to try to legitimize Haruka and Michiru's relationship for homophobic people. The article was redacted but it still left its tasteless mark on the history of the fandom in North America.
As for rumors that say Haruka is a man that changes into a woman as Sailor Uranus, much akin to the Starlights, this is false as well. In the manga, the Starlights are always women and simply wear male clothing as a form of cover in their civilian identities, much like how Haruka chose to wear the male uniform at Infinity Academy. Takeuchi Naoko was very upset when the Three Lights were turned into actual males in the 90's anime, as the sailor soldiers are supposed to be female at all times. If the Starlights are female, there's no way Haruka wouldn't be.