I believe the way it goes is that USR1 kills BSD dd. The Linux kernel doesn't have SIGINFO. GNU dd uses SIGINFO on platforms that have it, or SIGUSR1 otherwis

I believe the way it goes is that USR1 kills BSD dd. The Linux kernel doesn't have SIGINFO. GNU dd uses SIGINFO on platforms that have it, or SIGUSR1 otherwise. The default action for SIGUSR1 is to kill the process. So it makes sense that on platforms that do have SIGINFO no one would bother to override that default SIGUSR1 behavior.