Yes, it is more important at cycling speeds, as I simply stated as a fact originally. I didn't think it required any justification, but OK that you mention the basics there.
What I think you're neglecting here is that even though drag is more important in cycling it still plays a bigger part than you seem to realize in running. 8 0r 10% of his energy overcoming drag in a 5k. Keeping in mind that the runner has twice to three times the drag coefficient of the road cyclist, it becomes significant at lower speeds.
Wind direction, wind speed, and the rest of that plays just as much a part for the runner. So going strictly by pace you could be off by 10% - not important, perhaps, but no less important than needing precise power in cycling rather than estimating to within, say, 10%. It's funny, to me, the disparate "conventional" opinions between the two sports, utterly convinced that a power meter is a necessary training tool in cycling and equally convinced that it's irrelevant in running, even though objectively the reasons for those firm convictions are validly applied to either sport.
I'm more in line with @
Doge - it's a more specific need than most people realize - but if a cyclist believes that he really needs a power meter to train properly, then he's not really training "properly" if he's running without one.