It's part of a marketing strategy and OP is doing it right. I do sell gadgets (phone, laptop etc) and i make use of the pharse a "must use" even when i don't use those device so i see no hard in him using those words as far those videos and books are educational in regards to understanding blockchain and cryptocurrency.
When you sell the gadgets you are owning them, you checked them and verified their working condition before selling. You know the technical specifications of the device even you are not using them.
Here OP is suspected to know nothing about the books and topic that OP is recommending.