Nope, The gpgconf --kill keyboxd hangs too, if I see right, while waiting for agent:
$ strace gpgconf --kill keyboxd [...] clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f2d74fe2a10) = 3244 wait4(3244, 0x7ffc9836e364, 0, NULL) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)