Clients accessing a hidden service can establish their rend point in parallel to fetching the hsdesc
Right now the client goes through the process of fetching the hidden service descriptor, and once it's there, then the client realizes it wants a rendezvous circuit ready. It could instead do these two steps in parallel.
Now, the reason not to do it is that we can just cannibalize an available general-purpose circuit and we've nearly got a rendezvous point. And then Tor client will indeed already try to keep general-purpose circuits around. So maybe it is not worth the wasted circuit? I'm not sure.