Was just passed down my grandmother's e-ring. It needs some TLC from the years of wear (redip, cleaning/polishing) but I've never seen prongs set up this way before...
Agreed...I've seen this filled-in type described as "faux" cathedral, not sure if it has another more technically correct term.
But in any case, doing a Google image search on "three-stone trellis cathedral setting" brings up several images similar to OP's ring, as well as several with a true cathedral, like the one you posted, junebug.