I'm a little puzzled. I've subscribed to the tag access-vba but not to the tag vba. However, the emails I am getting show that the questions are simply tagged vba, not access-vba.
Is there an explanation for this behavior?
Ideally you'd at least be able to create and subscribe to a tag filter for just questions tagged vba and ms-access and get results similar to those you were expecting, but unfortunately it seems like there's no way to limit filter results to only questions containing all of the specified tags.