Before you comment anything about this being intended please notice this:
Original thread: https://support.riotgames.com/hc/en-us/articles/207884233-Hextech-Crafting-Guide
It is under FAQ.
So yes, this is a bug. What is weird is that even tho this is a bug, on the post-game screen it says that "You cannot earn chests or fragments on champions you do not own."
Please either remove the note from the thread or fix the bug and remove the message.