We often export WAB apps and deploy them on our web server because we need access to ArcGIS map tiles that are on a separate server and behind a proxy. That requires us to download edit the JS code to configure the proxy settings. It looks like all of the widgets that are exported contain files for multiple languages. Here's a screenshot from the 'Directions Widget' folder
When I downloaded our WAB app from ArcGIS Online, it contained 7365 files in 834 folders!. Even though many of those files are very small (each of the above files were 2-4kb), it takes a long time for us to upload all of these files to our webserver.
I understand the need to support multiple languages and I'm glad that ESRI provides such flexibility. But I imagine that most (nearly all?) organizations only need to deploy apps in 1 language, maybe 2 tops. I'd like to see an option to specify which languages are needed for your app, such as "en", "es", "fr". Then WAB would only export the files that are needed for the specified language.