Reverse charging in its current state is nothing more than a gimmick as its extremely inefficient, we need better density batteries to utilize this. I could see apple limiting the feature to just AirPods and Apple Watch at most, dont expect to start charging each others phones anytime soon.
I tried to charge my iPhone Pro Max from a Pixel 6 phone.....let me just say by the time I got my iPhone turned back on, I had almost two phones without battery....my Pixel 6 lost incredible amount of charge just to give me 10% on my iPhone...I could have just kept the pixel for the entire day up and running if I hadn't attempted to charge my iPhone.