Yes, true, one of the most brittle coral skeletal structures for sure.
It might take weeks or even months to drop off completely, but when it does consider letting it stay on the sand bed. Most people mount their Fox Coral to the rockwork, but their natural location is actually in deep, rather dimly lit waters with lower flow and situated horizontally on coral rubble piles/platforms on the sand bed.
Indonesian Coral Habitats
'Where is Fox coral found and collected? It is found in vast dense tracts on the seafloor bottom 33-35m down, mixed equally with free-living Goniopora spp. Other corals in smaller numbers consist of Alveopora, Sarcophyton, zoanthids, Sinularia, Euphyllia, and a possibly new species of Lobophyllia. Nemenzophyllia turbida is found in fields, sitting on the bottom with polyps facing upward. The colonies are mostly broken apart, and they are perhaps asexually populating these fields by bioerosion-induced fragmentation as no buds were seen on colonies. The entire area is bathed in silty deposits and sits perhaps a half-meter above the surrounding seafloor, a platform composed entirely of the dead skeletons of corals found there as silt and bioeroding organisms bury and erode previous growth. The corals are all free-living, none are attached.'
Based on the horizontal placement, low flow and silty surroundings, the coral very likely relies heavily on continual gravity deposited organic material.
I recently moved mine from the rock work (where I had it at a 30 degree angle and it barely grew) to the best approximation of this natural environment in my system. Since it's now horizontal, I can more effectively feed it (they are relatively slow feeders).