You need to burn thousands of calories every day. Most of the protein you eat should get burned.

By storing 10g of fat (90 calories, 3.5%-5% of daily calories) per day you accumulate 3.5 kg of fat after an year. By eating protein that cannot be utilized by your body fully (wrong amino acid profile) you are storing extra fat and build less muscle.

Whey protein most probably would bound muscle protein synthesis by methionine available, and make substantial (I think 40%) amount of calories from leucine in it to be converted to glucose. Two 33g servings of whey protein can be converted to 1g of fat, just from leucine alone.

Whether you store fat is based on whether you eat an excess of calories. Some protein being only usable as fuel is fine, because you need fuel. If that fat isn't being immediately burned, then eat slightly less.

> I learned that humans are apex predators a couple of years ago.

I'm afraid you're going to unlearn it, as humans are below big felines in the food chain.

If humans are considered apex(-ish) predators, it's because there's mostly nothing "above" us in the food chain. We aren't typical prey for any other animal, so we are at the top-ish.

It doesn't mean the diets of humans are biologically supposed to consist of huge amounts of meat.

Most apex predators are of course obligate carnivores. But humans are probably near the top because the use of weapons and tools makes us highly dangerous, so most land animals are wary of humans. Even many predators don't prey on humans for food.

(Although some large land predators do, mostly when they're desperate for food.)