Yes, they would be free.
Reminds me of what I tell everyone else about chicks, that is, buying the chicks is the least expensive thing about having a backyard flock. It's really your time and labor going into caring and tending the flock that adds up - at least if you considered your labor time as worth anything.
I know most people have advised not to get these "free" chicks, returned for whatever reason. They are probably right and i could be off base. But my thinking is that a store receives maybe 200 chicks, and a handful are not as perky as the rest. Will they survive? Maybe not.
Are they sick and infected - and the others shipped with them not infected? I would think that all chicks would either be free of infections or all have the same problems coming from the same hatchery. If infected, the "strong" looking chicks may not last very long either. I bought my chicks from our local Co-Op, and the guy who runs the chick program told me that a number of years ago he got infected chicks from a hatchery that they sold at his store. . Within weeks, customers were coming back saying the chicks died and had infected their existing flock. So he dumped that hatchery and now gets his chicks elsewhere. So I understand that the concern of getting sick chicks is a real issue.
Point is, I guess you have to be very careful about introducing any new chicks to your existing flock. In my case, my brooder setup in my garage is completely separate and nowhere near my backyard flock.
Unless that store is experiencing massive death reports of the chicks they sell, I suspect maybe these "free" chicks were overstressed in the shipping and/or maybe just a bit weaker than the others in the batch. I would take a chance on these "free" chicks myself, but I have over 40 years raising small animals and have had to deal with loss many times over. My chickens are not my pets, and I don't get that attached to them. That is just my way to cope with the loss of an animal when it does happen, and the very fact that chickens don't live that long even if healthy.
If you can celebrate the survival of a few chicks and not mourn the loss of most - or all - of these chicks, then it may work out for you. If you don't feel up to dealing with the expected loss of these chicks, then I would not get them, even if they are free.