[nescoiquid]

> But you'd still expect features to be getting implemented at a higher rate

Yes, I'm inclined to agree, but I actually haven't ever seen a study which compares the same project implemented in different languages to establish in toto the variance in SLOC. It could be the case that in the main for the same project the differences between languages wash out, as different languages may have different advantages and disadvantages that are more likely to tell on a substantive project.

What you suggest seems reasonable, but I simply don't know it to actually be the case.