So I had this weird moment in an gen 7 Ag match where my lvl 1 magnemite got hit by a critical hit precipice blades from primal groundon and sturdy did not get triggered. It did not go to 1 hp instead it took 72%. I tried replicating it in a friendly but without succes. I am assuming it was a bug, but I have heard similar things happen in the real games. So I am really sorry if this is not relevant. I saved the battle so the link wil be below this, thanks for checking it out.
https://replay.pokemonshowdown.com/gen7anythinggoes-1166391156-o6i7hayqnf4wa1ip2ne31zec043hoabpw
https://replay.pokemonshowdown.com/gen7anythinggoes-1166391156-o6i7hayqnf4wa1ip2ne31zec043hoabpw