Bit of a fluff piece with a weird title. Yes, GMs use "suboptimal moves" in their games, but the main reason is to take their opponents out of prep, and more importantly those lines are also heavily analysed by engines. They are specifically looking for imprecise moves that are only imprecise if the opponent finds the correct line, which could be 10-15 moves deep (so it might not be feasible to do over the board).

And this isn't something new. Magnus has been doing this for a few years now, after getting bored of facing the same over prepped opponents. He has mastered this technique, and showed that he's still the GOAT at mid to late game positions once the opponent is out of prep. But again, he's not doing this "randomly", he's studying when and where he can do it to temporarily get a disadvantage that will sort itself out later in the game. And engines are heavily used still.