Well, it's not actually that hard to make predictions on where players will recall. YouTube is filled with montage videos of blind ult snipes from people who are just throwing out an ult in the hopes of catching a player out. It's especially common near the buffs, baron, dragon and in the spawn. Just because someone managed to hit an ult blind doesn't necessarily mean they were doing anything dodgy.
It's also not 100% accurate to say that just because a player has very few matches with a champion in their match history that they have no experience playing them. While that is usually a good indicator, it doesn't account for smurf accounts or custom matches that do not run to completion.
He may have been scripting, he may have been boosting, or he may have just had a good support that got him ahead to where he could snowball.
Edit: I checked his match history. He has a ton of Ezreal matches and has been playing him for as long as the match history goes back. He just doesn't have that many recent matches with him, but he's got more than enough matches to know the champion's kit well and be able to land the skill shots. There's easily 100 matches on there.