Mining grammar points from a grammar guide is not required. But I did it, Khatzumoto did it too. If you decide to do the same, you may end up creating cards for very basic grammar, in which case delete them once you progress towards intermediate. I don't recommend mining every sentence like Khatz did, instead try choosing only the ones that look challenging. Don't add duplicate cards. The same grammar point should not already in your SRS, even if the example sentence is different.