I have used it many many yrs ago
and yes it works, as its still salt
but you have to be careful, as many of the rock salts I see in stores have things/chemicals added to it to help it keep from re freezing

and the main rason I switched was simply, pure salt has little help to the deer, where as a mineral block that adds something besides just salt )even if its honestly not much more)that can help the deer more, is more of what I was after
figure every little bit can only help
but yes I have used it in the past, just not anymore due to finding better things to use!