In the setting options we can choose if the file date tag is modified when we edit a tag but, I agree that it is logical that the inbox show a date modified when a file is added, of course, yes. So that is cleared
Now maybe I know the reason for the why I had all these files in my inbox but not in the library:
I think yesterday I tried the option "Manage folders" and then I did "choose filtered folders" to see how it looks like, maybe it was that ! It was probably that
Nevermind, I ended up deleting the library and then I have wait an hour or two just in case, to see if the population of files would occur again, it haven't, so it's all good
MB has such a great community, you're awesome guys and a special thanks to Steven, cleaver and talented software engineer