I don't concur. A few examples:

I was working on a iOS App that connects to a GraphQL API. All GraphQL are POSTs. POSTs aren't cacheable. I had to implement a client-side cache. Implementing a cache, understanding the pros/cons of an implementation, is an exercise in CS.

I was implementing an animation. I drew the animation out on graph paper and worked out the transformations using stuff I learned in my linear algebra and computer graphics classes.

And in general, thinking through the tradeoffs of Swift vs Objective-C or REST vs GraphQL or Ruby vs Elixir, etc, etc is an exercise in CS.

Unfortunately, we seem to live in a cargo cult world. Good enough for Facebook/Google/Etc? Good enough for us. ¯\_(ツ)_/¯