Would it have hurt the writer of 'The 37's' to take a few seconds to do a calculation before blurting we go "four billion miles a second!"?
Well, pretty much any usage of real distance units would muck it up since it's all "speed of plot" anyways.
Should they have just said "It'll take us 75 years to get home" and left it at that without saying how far away they were in LY units?
Believe it or not... 'speed of plot' is not an insult, to any of the series.
The writers and producers deliberately left a lot of things vague when working on the original Star Trek
(how fast warp speed was, how things worked, when the show took place). In hindsight, it was a brilliant thing to do. Probably one of the reasons we're still talking about it forty-one years after it was canceled. Plus it made it easier to gloss over the inevitable contradictions that would come up as you added more and more material to the Star Trek