Yes, some publishers are still quite big on fact-checking - and editing is often a very important stage if something is not very well-written but they want to publish it for whatever reason (big name, good story, good concept etc.)
It’s absolutely true that in publishing a blind eye is turned to the claims of gender ideology often not being factual or logical, and you do risk your job if you point that out. There are plenty of books, including children’s books, full of untruths about that because the ideology has widely captured publishing.
But this glaring error isn’t about gender at all, it’s a statement about political history and shouldn’t be controversial in any way. If you think it’s hard to find examples of openly repressive left-wing regimes you are simply clueless and know absolutely nothing about 20th-century history, not even at a basic general knowledge level. It’s on a par with never having heard of WW1 or WW2.
In the field of publishing I work in, I would absolutely spot and query it, and so would most editors I know, and If I wrote that I’m sure it would be challenged before it got to print.
This book was published by Virago, c/o Little, Brown, c/o Hachette so hardly a fly-by-night operation or dodgy vanity publisher. Shockingly bad.