>>52856078Since pokemon invoked the existence of a multiverse a couple generations back, you can say that G/S/C takes place in a different universe/timeline from HG/SS. Or you could just decide that G/S/C is 100% noncanon and is fully replaced by the similar-but-slightly-different HG/SS content. Either way the idea of steel types being " recently discovered" doesn't work if you allow for the type chart to be something that exists within canon rather than a game extraction, because then the nature of reality somehow changes as pokemon researchers discover things. The setting turns into madness where subjective reality trumps scientific rigor and it gets worse then harder you try to make it make sense. Best to just ignore the retcon.
>>52856150Ditto the above for gen 6/Fairy-types