The problem is that some sites don't display the fare classes. The good news is that MU's Y flights are all 100% MQM. I'm not aware of any that aren't so I'm not scared if the fare classes aren't displayed. If FM's fare classes are the same as MU then I guess I have nothing to worry about.
To be honest, I really odn't care about RDMs all that much. It's like 25%. MQM is way more important to me. I have a MQD waiver so it's not something I need to be concerned about either.