Thread:S3r0-Ph1i/@comment-39117874-20190620230932/@comment-36009152-20190621221715

Um, nearly there, the explanation was that 'Dinosaur', and similarly too obvious to the point they are not needed like 'Scaly', or 'Red Coloured' categories are not required.

What it means is that with categories there and established you should discuss with other users as to whether a new category is needed before adding it. If it is removed sometimes a stubborn unhelpful practice known as 'edit warring' can occur, but the best users choose better use of their time than that. Talk it out that is the ideal way, and if you feel the additional category is needed, show why it's useful!