Credo complaining public spec missing on a macro-generated function

gistfile1.txt

# Save this file as example.exs in the root of a mix project with credo installed 
# and [Credo.Check.Readability.Specs](https://hexdocs.pm/credo/Credo.Check.Readability.Specs.html) check enabled
# and run a
# ``` bash
# mix credo example.exs
# ```
# command to trigger the error
# or 
# get a .credo.exs file with the check enabled and
# uncomment the last line and run this as an escript with
# ``` bash
# elixir example.exs
# ```

Mix.install([
  {:credo, "~> 1.6"}
])

defmodule SpecMe do
  defmacro __using__(attrs) do
    for attr <- attrs do
      quote do
        def unquote(attr)(attr = unquote(attr)), do: Atom.to_string(attr)
        def unquote(attr)(attr), do: attr |> Atom.to_string() |> String.reverse()
      end
    end
  end
end

defmodule UseSpec do
  use SpecMe, [:ab, :bc, :cd]
end

# uncomment and run 
# elixir example.exs
# to see this stuff working
# UseSpec.ab(:ab) |> IO.inspect()
# UseSpec.ab(:bc) |> IO.inspect()

# UseSpec.bc(:bc) |> IO.inspect()
# UseSpec.bc(:cd) |> IO.inspect()

# Mix.Tasks.Credo.run(["example.exs"])