Mkjr, I do not question your one experience (and I assume that you have no OW saphire or Emerald staus?). Lounge dragons are often untrained or "lazy" and rules tend to be quite complicated especially with codeshares and the like.
However, the rules of OW are quite clear and the experience of hundreds of pax who have raised this issue in numerous threads in all the OW airline forums are moostly consistent with the rule. The "ANY lounge" only applies to OW saphire and emerald (status), not to J & F pax (cos). You might have your personal reading but I suggest that you look at various threads on this topic in many forums.