The makers of "Hive Alive" obviously have a good website. Anyone's questions can easily be answered there. When users are reporting back nothing but positive comments it points to this being a useful product.
Would you publish negative ones ?
The main sales pitch centres on seaweed extracts and their proven ability to promote healthy gut bacteria, We possibly neglect that sphere of bee health as it is impossible to measure or identify. I suppose we only see what their "guts" are like when they have problems with dysentery.
I believe that a balanced intestinal microflora is significant to the overall health of a colony and I've posted below a summary of a recent study which suggests that the colony "smell" which allows bees to identify colony members is less a result of genetic similarity and more connected to the sharing and resharing of food.
I think we have to be cautious about adding anything to the hive as this damages a finely balanced ecosystem, but I would hazard a guess that "Hive Alive" maybe helps to counterbalance the collateral negative effects of treatments and feeding used on bees.
https://www.beeculture.com/catch-the-buzz-gut-bacteria-key-to-honey-bee-id/