Maybe I'm looking at the wrong sections / using wrong keywords in the chart user's guide.
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The X in a flag for a intersection, waypoint or fix regardless of if it is a NavAid means there is a Minimum Crossing Altitude. An MCA present means you must be at or above a certain altitude when passing over the fix in the direction specified. This would provide obstacle clearance for that particular Victor airway. The MCA usually indicates a transition from one leg or section of the airway to another with a higher Minimum En Route Altitude.
In the case of the LLC VORTAC noted above, that altitude is 8500 feet MSL when traveling Northeast on the V6 Victor Airway. However, it does not necessarily apply to the other airways. In this case, it only applies to aircraft continuing on V6 or joining V6 going Northeast. The MEA for the upcoming airway section is 12000 feet MSL. Where as some joining airways such as V32 have an MEA as low as 8000.
This differs from the Minimum Reception Altitude. The MRA is used to ensure proper signal reception of the NavAid used to identify a fix. The fix will be on an airway. But the cross referencing NavAid used to identify the fix does not have to have an airway associated with it.