That happens in my town, but is notably rare in London exactly because of the planning rules that force the construction down into the basements.
The articles describe the basement amenities as little more thanan arms race between oligarchs.
One of the things the linked article does is fact-check the claims of all these other clickbaity articles that have been written on the situation.
I’m saying they’re bypassing the spirit of the zoning laws.
The reason they’re getting planning permission (and not bypassing the zoning laws) is because their construction retains the character of the neighborhood by building underground. I wish that was the case in my part of the world, and apparently yours.