Well, that's true and not true. On the ladder, where every game is (sort of) a one-off, you want to have a solid game, and it doesn't matter so much if it's a predictable "standard" game as long as you play better than your opponent.

But if you're a known player playing against other known players, or if you're playing best-of-N matches, it's valuable to have demonstrated flexibility in your play and a willingness to perform individually suboptimal strategies like early all-ins. If your opponent believes that you're capable of many different things, they will feel compelled to scout earlier and more carefully, and their options will be restricted slightly until they feel they can pin down exactly what you're up to.