I believe he is talking about this chart.
There are layer 3 switches in the chart but this is because those are the “lower end models” that Cisco has to offer. They can run as layer 2 switches and not utilize the layer 3 functionality. As switches have gotten more powerful layer 3 functionality has been easier to put into a switch. A big consideration of what switches you might use in a network is the size of said network. A tiny network might only need 2960-X’s for the core, distribution, and access layer. I hope this helps!
Thanks,
Scott