Think about it this way. Assuming you and your opponent have the same poke speeds and for some reason no one is using side-steps or crushes, if you choose to guard or fuzzy every time you are at disadvantage, your opponent will pick up on that and will either throw you with their heaviest throws/OHs or retaliate with a slow attack that has good guard frames or mix-ups since they don't fear being counter-hit.
Now consider that half the time you're at disadvantage you toss out a moderate-speed low attack. Well, now your opponent will want to avoid using throws, standing OHs, high attacks or any slow mid/lows as there would be a 50/50 chance any of those would fail and lose them that opportunity.
So by doing practically nothing but stupidly switching between a single attack and a guard, you severely limit your opponent.
In the hypothetical it seems smarter than always going on the defense. In the hypothetical, you are literally attacking from disadvantage half of the time.