[apparentlymart]

In this context, I think it usually means that the same rendering paths are available on both the client _and_ the server, whereas formerly it was often the case that the server was responsible for the bulk of the rendering and the client just made minor adjustments to the DOM in response to events.

I agree that it's a bit of a misnomer, but I can see why people would call it that given the path we took to get here: first we rendered almost everything on the server, and then it became popular to render everything on the client, but now we're finding that a compromise is best, and that compromise is easiest to achieve when you have similar technology on both sides.

("We" in the above is intended to represent some vague idea of the web development community at large, not any particular individuals or groups.)