From the last Dive, they were talking about how "Bin did it" isn't a reason to build an item in game. Meteos said, "Yeah, I've had that in scrims. Someone will just say 'let's try Malzahar' or whatever. I don't know why, LCK did it."
Those aren't the same. You can play things in scrims for the purpose of understand if/why they work. You shouldn't be building items in a playoff game purely because someone else did it.