Explanation of 待たされていました form in the Section 2-1 Inflecting needs to be revised

[Konstantin-Glukhov]

される is technically a passive form of the causative (使役) helper verb す
Since the causative helper verb す is not mentioned in the book, it is hard for readers not familiar with it to follow the example 待たされていました. It would make sense to re-write it as 待たせていました or add explanation of す to the causative section.

[Pomax]

Way more value in mentioning す than in pretending there are no verbs like the modern 五段 verb 待たす, derived as a conjunction in classical Japanese, but treated as a "normal" verb in its own right pretty much since 四段 stopped being a thing.