Fuego and GnuGo are provisional, so the human's rank won't change. The reason to play ranked anyway is to adjust bot's rating based on wins/losses so it has a reasonably estimate of strength.
RoyalLeela is non-provisional because it has been reliable enough it doesn't have the timeout issues the other bots sometimes have.
If you don't want to play ranked games to test things out, don't click the Ranked button?
Some people think all bots should be provisional forever, some like RoyalLeela being non-provisional, some feel rated game shouldn't even exist as an option for bots. It won't be possible to please everyone.