Yea, I’ve seen a lot of applications that were “designed” by a guy just sitting down and writing code.
And I’ve made a lot of money fixing them.
What’s the difference? Well, you can certainly use the word “build” to describe all the many discrete processes involved in the construction of an entire system. Certainly when discussing the project with sponsors or customers. But it’s more often used among my teams as the process (which is usually automated) of taking all the source code that the developers wrote and compiling it into the executables and deliverables that will be deployed to the servers or end-user devices.
When we want to be clear, we use the word “designing” to describe how a specific feature will be implemented, the inputs, the processing, the outputs and formats.
And during that design we ensure that the physical design — the libraries, technologies, and models used — actually fit the architecture we have standardized on, because that goes a long way to reduces the costs for support and maintenance.