I think the Cambridge Latin Course just updated their textbooks and one of the changes was to change the treatment of slaves to make them less objectified, so this bit seems plausible to me.

https://www.cam.ac.uk/research/news/new-cambridge-latin-cour...

> Enslaved characters were, in earlier editions, sometimes depicted in simplistic terms: as “happy”, “hard-working” or “lazy”. In the new edition, slavery is now depicted through the eyes of its victims, focusing on their anxieties and gruelling lives.