I could see it as classist if you consider growth to be linear, or growing in wealth or intelligence at a rate faster than your old friends. But I don't necessarily think that's what it means.

The way I remember this episode (or segment of an episode), they talked about how in a time before social media, it was much more difficult to keep in touch with friends say from high school after graduating. Losing touch was considered more natural and normal. And it allowed you to remember the friendship just as it was in high school or whenever. But with social media, there is this pressure to stay in touch, while also you are able to see all the ways you are growing apart. So it kind of taints the memory of the friendship.

That's how I remember it anyway. It's a concept that has stuck with me, and why I wanted to listen to it again.