If you're gonna have a discussion about gender benders, you can't do it without acknowledging Rumiko Takahara, and her work on Ranma 1/2. Literally the origin of the gender-bender genre. It did not exist before she wrote that series.
Ranma 1/2 was meant as a martial arts themed rom-com, primarily of the slice-of-life variety. It was leveraged entirely for comedic effect, but also occasionally the reversible gender-bending was utilized to explore gender roles a little bit.
This, of course, proved to resonate VERY strongly with certain audiences for a variety of different reasons. And then, Mushoku Tensei happened and popularized the reincarnation model of Isekai. Now, we have the single most logically sound way to transition a character from one gender to another. Only problem, this method is nowhere near as reversible as other prior methods in the gender-bender genre. Also, isekai gender benders are often not played anywhere even close to the level of comedy that prior additions to the genre were.
Just food for thought in terms of the history behind this phenomenon.
(My favorite in the gender bender genre is and quite likely always will be "Ore, Tsuintēru ni Narimasu" (Gonna be the Twin-Tail!!) It's just so ridiculous, and parodies so many things at once. And, the method of gender change is male-to-female magical girl transformation. So, it's also the most controllable and reversible. Plus, it has the added benefit of FOR ONCE having a magical girl who you would never suspect is a super heroine when in their normal un-transformed state. Who would ever suspect a boy is a magical girl?)