- in 2.4.x the general default for polyMesh::findCell was FACE_DIAG_TRIS,
  but this was changed to CELL_TETS for better handling of concave
  cells.

- in snappyHexMesh meshRefinement, findCell is used to define
  locations in mesh and cells for closer refinement. Using CELL_TETS
  causes an octree rebuild when the mesh has changed and this adds
  considerable overhead. For this operation, the faster FACE_DIAG_TRIS
  mode can be used instead.