While I didn't vote for Grotle, I do like playing Devil's Advocate to see both sides of the coin.
Grotle, like every other Pokemon, has access to Hidden Power which can be Fire. Also that Durant has Hustle as it's ability so Durant only has an 80% chance to hit with X-Scissor. Grotle also only has a ~20% chance to get OHKO'd by X-Scissor if it has full Defense and HP EVs, Bold nature and Eviolite and Durant has Hustle and Choice Band meaning that Grotle has a decent chance to live for 2 turns which it needs to be able to KO Durant with Hidden Power.
That being said, Durant can always run Swarm instead of Hustle and to be guaranteed a 2HKO and not have to worry about Hustle's accuracy drop.
Also while Durant can get First Impression which would ups it's chance of a OHKO to ~80%, Grotle can just use Protect on it's first turn and First Impression becomes useless.
Straight up getting into super advanced stuff like evs and all that way beyond anything I'm into. So the best I can do here is just in my mind imagine "sure there are scenarios where it can win, but in 99% of other scenarios it loses"
Like if you gave 2 ai trainers the pokemon and had them battle I'm confident in saying Durant wins every time unless it somehow just spams non damaging moves.