I just found some supporting testimony for a long-ago vexing question.
When I was administrator for the Hugo Awards in 1996, one of the Best Novel finalists* was Remake by Connie Willis. By that time, SF novels were tending very long, but Remake was short. Though published as a standalone volume, it made a small one.
Charles Brown of Locus,** the newsletter of the SF field, insisted to me that Remake was under 40 thousand words and thus, by Hugo rules (which were shared in this respect by most other awards in the field), it fell in the Novella category, not Novel. And indeed, in the Locus awards it was put in the Novella category, which it won (not surprisingly, being one of the longest in the category as well as being by Connie Willis).
But most of its Hugo nominators had put it in Novel, and every time I did a word count estimate on it, it came out over 40 thousand, so for the Hugos into Novel it went. Where (perhaps because it was one of the shortest) it didn't do very well.
I've always wondered: did I somehow count it up wrong? But I was doing a little incidental research in the ISFDB and found its entry. They think it's a novel, and the Nebulas (the award of the writers' group, SFWA) also classed it as a novel. So I'm in good company, and it looks more likely that Charles Brown was in error.
*I still tend to write "nominees" for this status and then have to correct myself. But since anything that even one voter enters on the nomination ballot has been nominated and is thus technically a nominee, and various unscrupulous people have exploited that, we now try to say "finalists" to mean the ones that got enough support to make it to the final ballot.
**Many people who knew him still call him "Charlie," the name he originally went by informally, but he announced many years before his death that he was giving that up and wanted to be called Charles even informally, and I've always tried to respect that.