I can think of a few reasons why there might be a difference between the tags "mining" and "miner", but I wonder if the difference is too subtle to be useful. What does everyone else think?
There appear to be about 200 uses of the tag "mining" and only 2 of "miner". The popularity sort of speaks for itself - the tag "miner" is not that far removed from "mining" as to make it useful by itself. I'd make it a synonym.