Opening an app doesn’t cause the cache folder to be created. I have been through the apps twice and the folder has not appeared. I deleted the folder around 1500 today and it came back at around 1700 according to the folder and file creation times. But I wasn’t using my phone at that time.
I generally don’t trust the permissions boxes as there are some apps like Smart Audiobook player or Files which do have access to the file system but show No permissions granted in the app info.
as for the location of the folder it is in the root user directory along with DCIM, Downloads, and Documents folders.