It's a trope from the days when you could still get vehicles with manual brakes with no power assist. As you can imagine enabling such a vehicle to go faster greatly increases the workout the operator is going to be getting to the point where if you want to drive aggressively in stop and go traffic the operator is the limiting factor.

I wonder how the 20 year old GT cars would do on modern tire construction and compounds?

Probably pretty good but not better than modern cars.

In the 2000s one of the car magazines tested top trim (big engine, race package, etc) classic muscle cars on modern tires and they put down respectable numbers, not better than 00s cars, but respectable.

Suspension and chassis stuff hasn't come all that far since the 90s so high end cars of that era should be able to handle very respectably compared to modern stuff. The differences are more apparent at the low end. Modern crossovers handle very respectably for what they are.

Obviously modern stuff will always win in a straight line because power levels increased massively over the past 20yr.

Are those numbers with threshold braking or engaging the ABS?

Not sure, but here's the sources:

The article with the Suburban data: https://www.caranddriver.com/features/a35048882/tahoe-yukon-...

Mustang and Camaro:

https://www.caranddriver.com/reviews/comparison-test/a151408...