Are you a software developer? The SDK is a “software development kit” intended to be a starting point for anyone wanting to create a customized version of the Zoom desktop client program. It doesn’t have all the features of the production Zoom client, but can generally perform all the functions needed for a meeting.
I consider the web client to actually be a workaround solution to be used when someone needs to use Zoom, but their IT department won’t allow the Zoom client to be installed. Two totally different use cases!