Yes but likewise, the motives and their future intent is unknown by a sub optimal move. So in a sense, it is similar to bluffing when you don't know the actions of the other person, deception is required to make yourself unpredictable.

This is why playing against a maniac (seemingly random and not respecting bluffs or equity) is very difficult because if they get lucky enough times, they are able to "break the game" by getting the opponent to be extremely risk averse OR take on more risks.

I believe this is what Magnus is referring to, its that making yourself unpredictable by questionable moves and no longer playing in a way that has been taught.

For example the common strategy is to go all in with strong pairs like AA, KK but someone beats it with a totally random garbage hand (52o, 37o) and does so repeatedly, no theory can help you win against somebody who is just repeatedly lucky and brash.