100% means that 100% of the intended features for the game are currently implemented in the game server code. The percentage says nothing about how stable the server is, how many bugs there are, or whether it’s publicly available. This has always been what the progress page was intended to say, although I understand it can be confusing because many people expect that information to be there.
There are plans to add pages describing each game’s availability and stability on the website [Enhancement]: Completely redo the "progress" page and add dedicated game pages · Issue #320 · PretendoNetwork/website · GitHub.