I happen to have the exact wording of that note as of 2020-06-16:
Note: Projects in this bundle are hidden in your library by default untill you first access them in order to avoid flooding your library. You can return to this page at any time to access any projects you wish to show in your library.
Note: We will be updating this page soon, we know it’s difficult to navigate so many games. We know you want a button to add show everything in your library. No need to reach out. Any new games added to the bundle will automatically show up here. Thanks!
While they did not fulfill on updating the page “soon” I would have been surprised if a button that add everything from the bundle to a user’s library - based on the context of the first note and that it would ruin the usefulness of the personalized recommendations for those who would have clicked said button.
Whatever might or might not be implemented in the future would probably be more along the lines of filtering and sorting.