Crossreferencing DynamicSupervisor and Registry init spec is wrong. · Issue #181 · elixir-horde/horde · GitHub here for other readers.
We use Horde.Registry and have this same issue, ended up adding a .dialyzer_ignore.exs containing:
[
{"path/from/your/error/message", :callback_type_mismatch, line_number_from_message}
]
