I think that the 1k resistor is to help if there is an impedance interaction between the two devices wired to the outputs.
I don't have the extended manual, but in the stock manual, page 33 the 220 ohm CC resistors are soldered as close to the tube socket as possible. At the bottom of the page you can see that the destination grid from the first triode's plate has the resistor right up against it. The manual may have been updated and the pictures not where I am calling them out.