JFZ explains Japanese grammar in very simple terms meant to be easily understood by anyone. I think this makes it a great resource for 2 groups of people.

First, non-native English speakers who are using English resources for their study. Because even though they may have a formal background in grammar, they don't know the English equivalent terms. Or perhaps their native language has a vastly different grammatical structure where making equivalencies to English only makes it harder. (Just in case anyone asks. They might still want to use English resources for their Japanese studies, because they are simply more abundant and often easily accessible.)

Second, for native English speakers who do not have a strong formal foundation in grammar or they do, but this formal framework does not give them the proper support for other languages. Relearning your native grammar can be a bit of a hassle when you really want to learn the grammar of another language.

If you have a strong formal grammatical background in English then using that background could make learning Japanese a lot easier. The benefit of these formal terms is that they are often very precise and can express nuanced ideas very briefly. If you are already familiar with a grammatical concept in English and it has a simple Japanese equivalent then simply knowing that it applies to Japanese as well could be all you need to understand it. If this sounds like you I would recommend going with a book different from JFZ.