They expect to have six million people on the new city. If six million are elite, then they have a pretty good ratio of elite to commoner in Cairo.

Anyhow, lowering Cairo’s pop by six million should make it more livable traffic and smog wise.

The Cairo area was previously projected to grow another 6 million people in the next 12 years.

https://www.macrotrends.net/cities/22812/cairo/population

It will take longer than 12 years for this new city to reach 6 million people. So what will happen is the population growth will slow some in Cairo; there will be NO population decline there.

Lowering population is not how cities become better. Building more floors and more public transit is.

Not if it's overcrowded and unhealthy. Cities improve by obviating slums/shanties and overdensity and by modernizing.

"overdensity" as people per land area or per floor area? Because I pretty firmly believe the former doesn't exist.

You're going to believe the numbers of what is essentially a vanity project?