Yes, of course it uses the exact same blockchain as Steemit. It is built into the Steem blockchain. That is the whole point, the two are integrated. . I'm sure at some point they will separate Zaps and Steem posts, but for now they show up together.
Zappl is still in Beta, just like Steemit is still in Beta. Of course there are going to be issues. That is the risk you run being on the ground floor of something new.