function isOctreeSubdivision( tile ) {

	return tile.__implicitRoot.implicitTiling.subdivisionScheme === 'OCTREE';

}
Structure almost identical to Cesium, also the comments and the names are kept
https://github.com/CesiumGS/cesium/blob/0a69f67b393ba194eefb7254600811c4b712ddc0/packages/engine/Source/Scene/Implicit3DTileContent.js