Yes and no.
WordPress is inherently web content management system. Whatever you do with it is web development since end result is, well, a web site.
However not all of WordPress is web development. Not all of web development is something that you typically do in WordPress.
As you grasped WP is strong at back–end and contains immense amount of functionality, as well as means to produce a lot of markup server-side. This is good since it saves you from all that work.
But the other side of the coin is that WP is kind of set in its ways. It is a legacy framework and “newer” (or even years old really) techniques (such as dedicated template languages, JS frameworks, and so on) are often under–explored in it.
In a nutshell starting with WordPress development does expose you to considerable amount of generic web development concepts (depending on what exactly you do with it), but it won’t be exhaustive and at some point you will have to look beyond WP to make further progress.