I think Intelligence Level is based on how little you need to think to get the most effect.

When you think, you are exerting energy.

When you memorize and remember, you are exerting energy.

If you have to think and focus on every little thing, that is like typing by looking at a key individually and making a conscious choice to press it, while speaking the key out loud. This is usually used as a joke in popular media at the expense of the elderly, as a stereotype.

I'm not looking at my keyboard.

I'm barely even thinking about my hands as I type.

Gaining this ability was an increase in my Intelligence Level.

Learning to bag groceries at Shaw's as a Teenager without thinking was an increase in my Intelligence Level. It happens through repetition and optimization.

I think this is the point of Rote Memorization.

The point is to get those Keys in your Brain so you can type those Keys without thinking, giving rise to concepts of higher complexity with less energy exerted. These complex concepts are generated organically, and certain organic processes can lead to predictable results.

Predictability is good in this context, because then that Complex Concept can be relegated to a single Key in your head.

Type on Keyboards of Higher and Higher Layers of Abstraction as your Intelligence Level increases.

If you need precision, then use tools.

Use references for exact values.

The fast typing in your head is not going to provide the same precision as an Excel Spreadsheet full of Active Formulas.

It took a certain Intelligence Level working at a certain Layer of Abstraction to even get to the point of Leveraging Excel.

Being told to use Excel for Leverage, and coming to that conclusion yourself are two different things.

One is based on Obeying Orders, and the other is based on Thinking, through an Autonomous Organic Internal Process of Logic Assembly.