The evacuation test configuration is be the densest possible configuration - the aircraft will be certified to carry that many passengers based off this test.

For instance, the A380 evacuation test had 873 people get out in 90 seconds (https://www.airbus.com/newsroom/press-releases/en/2006/03/a3...), and I don’t think anyone flies a 800+ seat A380 today. I believe the densest A380 is the Emirates Regional configuration with 600 seats.