Hi Mario,I think you touched base on an important point and I will try to explain this using an example from home appliances industry
Fabric Care Product Line -> this is the high level product line that contains products that are delivering the benefit of caring for the customer fabric and let's focus on care here so means everything from washers to dryers to washer dryer to twin tub ... etc.
Frontload Washers Product Category -> this is all types of front load washing machines grouped Into a single category and this category is part of the fabric care product line. So we are speaking here for a category containing all different specs that fulfill the description of fronload washing machines.
in some companies they group different categories together so for example some companies group frontload washers and washer dryers together and in some companies they keep them separated. It depends sometimes on the company's structure and sometimes the two categories are small separately in financial terms that they need to group it under one for efficiency and if the market itself is small for both, that's another reason for grouping the categorieswhen we speak about product platform, it means products sharing the same platform, so forexample as mentioned in PDMABOK , Volkswagen and audi TT share the same platform (structure) but they are sold as two completely different products with different segments and different customersI think the definitions that are presented in this book are not wrong but they are defining these terms in a different way and I believe it is not wrong to define these terms differently even among industries, if you keep one hierarchy same in your business.I hope this helpsBR