Computation (in the context of webpages) indicates JS to me, though they concievably could mean DOM construction. I'm fairly skeptical that transmitting a serialized DOM and unpacking it could be more efficient over mobile network connections that is using our time-honored DOM serialization, HTML.
I do hope I'm wrong, as I can't see how this sort of proxy can be healthy for the web, but I don't think my speculations are out if the realm of reasonable given the information.