ldm aka pop instruction for ARM affecting pc register should be classified as CS_GRP_RET, because, well, it's a control transfer instruction, usually used to implement (optimize) return from a subroutine.

Without cases like that, Capstone's instruction classification isn't much useful, and needs to be worked around in adhoc way on app's side. For example, for a recursive traversal disassembler, properly classified instruction are of utmost importance. If return insns are misclassified, a disassembler may disassemble what is not instructions.