I think what the OP means is that the webapps have changed application model from client side to a more server side approach. UX needs to change across platform

I think what the OP means is that the webapps have changed application model from client side to a more server side approach. UX needs to change across platforms (devices) yes, but the number of versions of application "out there" is just one (or a few, unless you're doing split testing).