I'm not discounting your own experience, but in your anecdote you acknowledge that got you act together 2 years before anyone in this program would get the money. An example of a 16-19 year old being immature is not a good argument that 21-23 year olds aren't mature.
There's no point getting this in the details of my personal experience but I _started_ the path at 19 because I ran out of money. I was still doing incredibly dumb and destructive things until 23.
I really do think this program will help a lot of foster kids. I just wish we could acknowledge that stipulating how the money is used will prevent worse outcomes for some. Free money will give some of these kids the resources to destroy their lives because the money isn't their main problem yet. Both groups of people matter and I want to see programs that don't ignore the negative side effects of free money.
Means testing absolutism doesn't need to be the hill people die on. First we need take care of the people, and then we can figure out the most efficient way to administer it.