You're seeing everything that is available. For both of those providers (I just checked both), the posts you cannot see are just posts that were removed. Things are commonly removed if they are duplicates, or violate forum guidelines. For providers, they frequently have weekly/weekend update posts that need to be removed, so that's why you will see the higher post count but no results when you search or use the "find more posts by" functionality.
Originally Posted by RocketSurgeon
Understood. I was looking for any info about them, not just their old availability posts.