There is a fundamental difference between SEO & SEO Web Design
Quite simply, SEO is defined as an ongoing process that should be continuously performed. SEO, however, entails SEO Web Design at the outset, which is the process of properly structuring and programming a website through a series of on page optimization techniques, and should always take place prior to the ongoing work such as landing page creation, link building (expertise), continuous code & content optimization, search engine submission, and other techniques which define the broader parent category of Search Engine Optimization.
The best analogy to describe the fundamental difference between the two is to imagine SEO Web Design as the process of engineering and building a very highly sophisticated boat, taking it to the dock, and setting it to sail in the ocean. On the other hand, ongoing SEO is equivalent to not only building the boat, but also staying on board to staff and captain the ship in the open waters of the sea.