> Every ~3500 calories under maintenance will result in 1 lb weight loss

If you are managing to lose pure fat, this is true; in reality, it probably won't be. Its more like 600 calorie deficit per pound of muscle, and, ceteris paribus, the greater the calorie deficit, the greater the proportion of weight loss that will be from muscle. (OTOH, the more overweight you are, ceteris paribus, the greater the percentage of the weight loss that will be from fat, so if you are very overweight, then a very aggressive calorie deficit is more tolerable than when you are less overweight.)

Losing muscle is more rapid weight loss than losing fat, but its generally not what people seeking to "lose weight" really want, so its important to not overdo the calorie deficit (what "overdo" means depends on how high your body fat is currently, various things that vary from individual to individual, and to a certain extent what the exercise pattern and particular diet pattern is that you are doing, since that affects maintenance of muscle mass.)