[yamtaddle]

Eh, in this case I don't think the story hinges on keeping that secret, and if you know what era of sci-fi the story was written in you'd be nearly certain you're getting the "shocking twist! (but not really a twist)" ending anyway. The alert, seasoned sci-fi reader would be more surprised by almost any other ending than that one, really, in a '50s story of this sort.

Same thing Asimov usually did—a shower and/or stoned "what if...?" idea turned into a short story in a straightforward way—except Clarke took the extra step to, like, write actual characters and draw a setting and maybe even establish tone and mood beyond whatever the literal plot itself necessarily conveys.