Forgot to save & upload replay, but here's a log of the situation I'm curious about.
(Gen 7 Random Battle)
http://pastebin.com/NE7tdf8j
My understanding is that currently in Gen 7 random singles, all Pokemon are at Lv75 (Lv73 for Ubers) with 31 IVs and 85 EVs in everything (unless using Gyro Ball, etc.) and neutral nature.
Opponent had no Zoroark, Tailwind, Choice Scarf, Slush Rush, Prankster etc.
So (Thick Fat) Walrein with a speed of 141 should have outsped (Snow Warning) Aurorus with a speed of 131, but Aurorus attacked first in Turn 4 with Encore.
Any ideas on how this is possible, or is this a bug?