In the traditional approach to sequencing summarized by Sri Krishnamacharya,
prone back bends always follow the standing postures to make sure that whatever you have done to your lower back / sacrum area in standing could be neutralized via symmetrical prone poses.
We do some poses in the upright position, some in
prone (on the stomach), some in supine (on the
back), we
bend sideways and even stand on our heads.