>>58563271
Everyone getting access to an extremely powerful tool will still benefit some Pokémon more than others. Pokémon that were already strong are typically in the best position to benefit from increasing the power level.
Many Pokémon already had a stat distribution aligned with their Type so the Physical/Special split didn't change much for them, while Pokémon like Gyarados and Salamence benefited tremendously.
For most Pokémon, Tera provides roughly the same benefit and its once-per-game nature incentivizes using it only on Pokémon who gain the most value from it. Given the option, a Pokémon like Ogerpon, Volcarona or Regieleki is far more likely to benefit from Tera than any other given Pokémon who can't utilize it as effectively.