http://xmpp.org/extensions/xep-0115.html#ver-proc
section "5.4 Processing Method", bullet point 3.6:

> If the response includes an extended service discovery information
> form where the FORM_TYPE field is not of type "hidden" or the form
> does not include a FORM_TYPE field, ignore the form but continue
> processing.

Wocky does not respect that. In wocky/wocky-caps-hash.c wocky_caps_hash_compute_from_lists():
      field = g_hash_table_lookup (dataform->fields, "FORM_TYPE");
      if (field == NULL)
        {
          DEBUG ("Data form is missing FORM_TYPE field");
          goto cleanup;
        }
Then, it returns NULL, and 
src/presence-cache.c _caps_disco_cb() considers the hash to be bad:
      computed_hash = wocky_caps_hash_compute_from_node (query_result);
      if (computed_hash == NULL)
        {
          DEBUG ("Unable to compute caps hash for '%s'.", jid);
          trust = 0;
          bad_hash = TRUE;
        }