If they are filled with resin, it is a high density resin used solely to add weight (same as the lead).
It will still show up differently in xray. I could determine whether that resin was poured before the original inlays were made, or subsequently.
Unfortunately, I cannot show the xrays in public at this time, as I have explained before.
However, if you give me a specific example of an original resin filled chip you are referring to, then I will try to elaborate.