In Ireland and other European countries they literally have to 'cover up' the Breakfast Cereals in the 'American Speciality/Import' section due to their misleading nutritional information and/or child targeting.

For example, American formulation PopTarts have to legally cover up the claim on the front that they are "a good source of nutrition" and another sticker on the back with a factual nutritional breakdown, as is mandated by most EU members.

Roughly the same calories as the McMuffin but half the fat, twice the fibre, and 50% more protein. https://www.mcdonalds.com/ie/en-ie/good-to-know/nutrition-ca...

As for your 300 calories contention - 300 calories of scrambled eggs or steel cut oats would do me fine to get through a morning. 300 calories of McNuggets would not conversely. I'd imagine most of that has to do with satiating fibre, protein and fat therein.

Now I'm thinking I might try using it in an egg sandwich for breakfast and see how it is.