supports
true when one buffer object may be bound to both GL_ARRAY_BUFFER and GL_ELEMENT_ARRAY_BUFFER over its lifetime. Desktop GL / GLES / iOS allow it, so the 3D Tiles path packs vertices + indices into one buffer bound to both (one mmap/primitive). WebGL forbids rebinding a buffer to a second target, so there callers keep indices in a dedicated GL_ELEMENT_ARRAY_BUFFER. true here; the WebGL backends override to false.