Guessing is guessing. Planning is guessing PLUS coming up with viable reactions to what might, or is likely to happen — doing some of the cognitive processing ahead, instead of deciding what to do when the ball is already in the air.
I get it, following a plan when my guess was incorrect is not smart. And tweaking a plan mid-air can be great, too. But I think saying that planning is “just” guessing goes too far and fails to acknowledge an important part of planning is knowing ourselves and thus knowing our options — regardless whether our guesses turn out to be right or wrong.