This is a misrepresentation. Development or maturation of the brain finishes around 25 years old. In this context, "development" refers to the completion of the adult form of the organ. The ongoing "development" that this blog post refers to is more accurately described as neuroplasticity. There is an ongoing potential for the brain to create new connections and reinforce existing ones throughout life, but the actual mature form of the frontal cortex is not complete until your mid-twenties.

Another way to explain this would be to use breasts as an example. As a biologically female girl goes through puberty, her breasts grow as her body develops mammary tissue and the surrounding/supporting structures. This is called secondary sexual development. If you used the word "development" the same way that blog post does, then the changes to the breast throughout adulthood (such as milk production, skin sagging, loss of adipose) would also be called "development", but that doesn't make sense when we're talking about development of sexual characteristics. Those are ongoing changes to the breast, but it is not the same thing as the initial development stage that is equivalent to the initial development and maturation of the brain that finishes in a person's mid-twenties.