Suet in ‘The Jewish Manual’

Does anyone know of an explanation (or where to find one) of the presence of suet (now identified with chelev and treated as non-kosher) in many of the recipes in ‘The Jewish Manual’? The preface explicitly mentions that previous cookbooks (not geared towards Jews, as this was the first English-language cookbook published) are less useful for the Jewish kitchen because they contain forbidden foods, so clearly there was some concern for the laws of kashrut.

Link to the book, from 1846, for the curious: https://www.loc.gov/item/88180014/

Thanks for any and all information on the topic!