That is AWFUL!
I've never heard of that!!! and I don't understand it!
It's one thing to just flat out tell you they didn't want to place the cats with you. OR they could have said "We think you're a likeable person but the home situation isn't ideal." or "There are other candidates who we think would suit the kittens better." but there is absolutely NO reason to string you along like that and lead you to believe you are getting one of the cats.
This was just hurtful.
I don't understand it at all and I hope you are able to find your kitten really soon.
Big hugs!