>>25215841Let me answer the second question first because that's easy.
Yes. In fact, it would be worth it even if stall didn't exist to begin with.
The first question's answer is less because it enables stall (although that's a big enough reason to take it down right there) and more because, to be blunt, Steel resisting 10 types and having immunity to an 11th is just stupid. It just warps team building around it to a ridiculous degree. You want to run at least one steel type, you want to run counters to the big steel types, you want to have your Pokemon have at least one move if at all possible that isn't walled by most steel types... Steel warps the metagame around itself to a ridiculous margin, and it shows in the usage charts in OU on down (December 2015's usage rankings were such that 45% of all teams ran at least one of Garchomp or Landorus-T; both of them are Ground-types that thus hit most steel types for SE with STAB moves).
So TPDP cut steel down to size in the defensive department and made up for it by giving it the SR equivalent and making it a great offensive type. Steel's still very good and something to keep an eye out for, but it's nowhere near as dominant or important in this game as it is in Pokemon.
And that's a good thing for balance. And a balanced game is one that's more likely to be, well, fun.
Pokemon Steel having 10 resists + 1 immunity is not fun. Puppet Steel is more balanced and thus more fun.
Plain and simple.
