This, to me, is another reason why employing a feedback cycle and only relying on those estimates as a first approximation makes most sense.

The estimates won't take into account how dilligent you are: do you estimate how many meatballs there is per 100 calories, or do you guesstimate based on measuring once? do you count the calories in your sugar free chewing gum (it's certainly not calorie free)? do you measure out the amount of ketchup you put on your food and count the calories? And so on.

With a feedback cycle hopefully you're roughly consistent, and if you adjust on a weekly basis based on how you're doing you'll hopefully also counter-act your own self-sabotage (e.g. it's oh-so-easy to subconsciously take more of anything you've decided doesn't need measuring, like the above mentioned ketchup, or find yourself suddenly chewing 10x as much chewing gum...)

(at the same time, one of the benefits of these shakes certainly is that if you adhere strictly at least for periods, you take dilligence out of the picture; though you still need a feedback cycle, as e.g. differences in how much energy you have can easily affect your activity levels and so change your rate)