Early on in the game (July, August 2016), higher mons in the pokedex all had 15 attack IVs when caught in the wild. So most dratini family and eevee family had 15 attack. Many were 80% or above as a result.
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Yep. I caught a 100% Eevee and a Snorlax that chances are would not have been 100% without the bug.
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This is where early players benefited but now its fixed and you can catch a 0% IV dratini.