The Humble Monthly February bundle contains an "exclusive sneak peek" of Hollow Knight. Is this a demo? Is it the full game in an unfinished state? If it is currently unfinished, will it be updated when the game is finished?
They are not the full games, and usually consist of a demo to play.
Here is a quote about a game listed as a "sneak peek" back in the February 2016 bundle:
"This sneak peek demo is a bite-sized taste of our new game Planetoid Pioneers, which we will ship on Steam Early Access on April 15th this year." - Data Realms
It is possible that they are demos of a finished game, which usually means the developer didn't want to give away the whole game to HumbleBundle, or it means that it is in fact an unfinished game and it's a genuine sneak peek at a product they intend to release eventually; however, if they do not specifically state that you will eventually be given the game, you will not be given the full game upon release.