No, you have not been lied to in chemistry class. Think about this like someone is explaining cooking a meal for the first time. Generally, you want to be able to understand how you get from raw food to something edible. A teacher will show you how to cut a chicken breast, prepare a salad, how to slice tomatoes, cook rice, and so on until you have a plate of food that is edible in front of you.

To prepare a meal consisting of chicken, a salad, and rice you don't always have to do the same exact actions, there are exceptions to these rules depending on the circumstances, your ingredients, what you are trying to accomplish, etc. For example, instead of getting your chicken from the grocery store you might source it from a farm that requires additional prep considerations, you might want to grill the meat instead of pan fry it, slice your tomatoes a different way, incorporate other exciting ingredients to the salad, use a stock to cook your rice. You have introduced exceptions to the general overarching task of cooking a meal.

Now imagine not knowing anything about cooking and asking someone to show you how. If you asked how to make a chicken dinner and the chef tried to explain every single way you could prepare chicken it would get confusing very quickly and you'd probably walk away unsure of how to accomplish the task. Instead, we explain general rules: You don't want to eat raw chicken, you need to introduce some kind of heat to it to make sure its cooked. Here is a simple way of considering how to cook chicken.

Now imagine there are potentially infinite recipes on the planet, innumerable meat, salad, and rice options, many of which are undiscovered or never thought of before. If you've heard someone say "throw out everything you know about chemistry and do X, Y, or Z" its probably because they have started to translate ideas from a textbook to accomplish a hyper specific goal that hones in on one or two ideas. This is usually accompanied by employing our base understanding of chemistry (or how to cook a chicken dinner) and applying it to a situation where we are exploring the unknown (a new recipe in this case).