bundle adjustment and manifold

Question

In the example bundle_adjuster.cc from ceres-tutorial http://ceres-solver.org/nnls_tutorial.html#other-examples, there is a option --use_manifolds which can only be used with --use_quaternions. If --use_quaternions is not specified, it defaults to axis-angle for camera pose. My question is: in the axis-angle case, does the ceres-solver use perturbations in lie algebra to perform optimization? If it does, why the --use_manifolds is not applicable in axis-angle case?