This is addressed in TFA. In many cases, attempts to create a simplified version of a game just teach bad habits; strategies that work in the simplified game might be not just suboptimal when the full set of options is available, but actively counterproductive.

But I dare say many fans of "heavier" games - especially ones with more of a simulationist bent - would disagree that having fun is sufficient.

Ultimately the fun of a heavy board game comes in having interesting decisions to make and executing your strategy.

So the nuances can really matter. Even if you get the rules right, you don’t realise the importances of something until you play once or twice.

It's iterative.

You're not going to learn a full complex ruleset in one sitting.Having a one page quick start of the game structure, allows you to get a feel for it before coming back for a deep dive.

Your brain has a foundation to build on when you read the ful complex rules - it wont feel like your brain is maxing out at 100%.