Yes
Yarn build creates a build in the build folder. Not the dist folder…
I have no idea why your yarn build did something else.
As per https://github.com/twitchdev/developer-rig/blob/master/package.json yarn build calls https://github.com/twitchdev/developer-rig/blob/master/scripts/build.js which builds the developer rig for release. It’s nothing to do with packaging your extension itself.
Rechecking your screen shot. Most of the contents do not match the layout of https://github.com/twitchdev/developer-rig
So in summary, I have no idea what your yarn build has done as it does not match the developer rig