Milk Chocolate has milk solids (dairy milk, that has let the water evaporate) so I assume that is what they are replacing in these things.
For those that have dietary issues with lactose etc I could see them being a market, but the general treatment of dairy cows is not a huge inhumane issue as a need for an alternative is bs... Most Dairy Cows have a crazy cushy life in spite of what the animal rights activists claim..
Go check out this guy if you believe the animal rights crap...
https://www.youtube.com/@iowadairyfarmer6299
Hershey’s decided to go woke, if they had marketed it as lactose intolerant version, you wouldn’t see the uproar.