`DType` here is an atom because of `erlify_bucket_prop` [1] so using`"sets"` and `"counters"` as the `datatype` value does not work. Only ones in the `?MOD_MAP` in `riak_kv_crdt:to_mod/1` do. Modify that function to work on the plural atom versions as well (or add special handling to `erlify_bucket_prop` [2]) maybe?

[1] https://github.com/basho/riak_kv/blob/develop/src/riak_kv_wm_utils.erl#L393
[2] https://github.com/basho/riak_kv/pull/708#discussion_r7143687