I've always thought that Gyro Ball was designed as the first iteration of Electro Ball but then someone pointed out all the Steel-Type Pokémon at the time (and largely still to this day) are slow asf so the move would suck
Not sure it makes sense because the most logical thing to do would be to re-type it rather than switch it to slower=more power, and that's exactly what they did a gen later with Electro Ball. Even still, though, the lack of sense the flavour makes with its current mechanics makes it feel like SOMETHING weird happened there.
And it was introduced in the same gen as Iron Head, whose secondary effect is a flinch chance and therefore only procs by going first. And Bullet Punch, a priority move. It almost does seem like Game Freak forgot Steel-Type is slow while making Gen 4's new moves at least until late in development lol.
Orrrr, here's a wilder possibility, it's all Bronzong-centric Trick Room marketing. Iron Head's flinch chance is to give Bronzong a cool "I can flinch you because of Trick Room!" angle to sell the Trick Room concept more, and Gyro Ball suddenly becomes a powerful fast moving attack under Trick Room meanwhile the flavour kind of makes sense. They somehow didn't consider that people would just use the attack outside of Trick Room or something. I mean, why else would you minimise your speed IV and get a -speed nature unless you were using Trick Room? To make the fast spinning attack stronger, that doesn't make sense??
Now that I've thought of it that's my headcanon
Random other weird thing I noticed looking at it, Staryu has always learned Gyro Ball by level up since Gen 4, but Starmie only learns it by TM and not by level-up. Strange choice, both of them are fast and neither of them are balls. Every other mon to learn the move by level up -- besides Bronzor and Bronzong themself -- are very explicit balls or are frequently depicted rolling up to become balls besides the later learner of Dhelmise (and kinda Varoom and Revavroom but wheels = balls seems fine to me).
