Clement’s later novels included females because people had pointed out to him that his novels had no females in them. To be fair, his work is not ardently sexist; it was just often focused on a group of scientists going to an alien planet to study the aliens ... and at the time Clement was writing, "group of scientists" largely meant "group of male scientists". There are female characters in “Iceworld”, and also in “Needle”, but those are set on Earth (with the aliens visiting us), where a complete absence of female characters would be a bit glaring. I think 'Needle' would be an interesting book to make a film from ... and (spoiler alert) given that the aliens are just amorphous blobs that live inside the body of a human host, it wouldn't be that expensive to make. If it had been the point of the book, a space-mission with fewer than 40% female crew would have been a different story and, concomitantly, much longer if added to the voyage to Mesklin. The humans are there as a backdrop for the Mesklinites and have to be as schematic as they are to fit the word-count. A space-mission with a few women would have been a good premise for a story (see the cover-story for that first issue of 'Universe' I mentioned in a post a while back) but akin to something like a woman accompanying Shackleton to the Pole. Who knows how many stories like that were spiked because of John W. Campbell's notoriously prissy secretary?
On the other hand, "Through the Eye of the Needle" is, if anything, more filmic than the first book. Well, the hero of “Needle” had a mother, though she only got a bit part.
But this wasn't unique to Clement. Eric Frank Russell was much the same, though in racial matters he was quite advanced. In Arthur C. Clarke's “Earthlight” the hero's wife is mentioned a few times, but never appears on stage. It was much the same with Verne and Wells, where Weena in “The Time Machine” is the only female character I can think of.
NB: I always enjoyed the SF of Hal Clement. Then someone pointed out to me - after I had read a few of his novels without noticing it - that his novels contained no female characters at all. Untrue. 'Noise' and 'Still River' off the top of my head. And the male pronouns applied to Barlennon and 'his' crew by Lackland/the narrator might not apply. I wonder why “Mission of Gravity” hasn't been optioned by Pixar. Admittedly Barlennon's a bit like Mr. Krabs from 'Spongebob' but maybe a character who communicates with farts is a bit advanced for Disney's shareholders.
SF = Speculative Fiction.