The use case is very simple
My evernote use is about 10 years old (at least), and has about 15 notebooks in it, i create a new notebook per project
I want to see all the tag-soup that is specific to the a certain notebook, and i have no way to do so, instead i can see all the tag-soup af ALL the notebooks, some of which are projects that have ended and are archived, others are personal, professional, research, DIY, design, etc.
I can view the pages in the notebook and they are filtered by notebook so i can see only those appearing in this notebook
I can search for words in the text of the notebook, and this too they are filtered by notebook
I can see all the tags i have ever added to my account, which is ALOT and include MANY notebooks, MANY MANY projects including DIY projects, work projects, etc... I do not understand the usecase in which i need to see all the tags i have ever created vs filter tags by notebook that appear only in certain notebooks ?