[johnnny]

t's a limitation imposed by the ping programme itself, it'll refuse to use very short intervals if you're not root. This is documented in the man page. Or, use the source, Luke:

https://github.com/apple-oss-distributions/network_cmds/blob...

  case 'i':  /* wait between sending packets */
   t = strtod(optarg, &ep) * 1000.0;
   if (*ep || ep == optarg || t > (double)INT_MAX)
    errx(EX_USAGE, "invalid timing interval: `%s'",
        optarg);
   options |= F_INTERVAL;
   interval = (int)t;
   if (uid && interval < 100) {
    errno = EPERM;
    err(EX_NOPERM, "-i interval too short");
   }
   break;

And if you keep looking, Apple's version of ping keeps track of the number of sent and received probes, but does not keep track of the largest difference between the sequence nubmer of sent and received probes, so it will not print the same "pipe" value as the iputils version of ping (ie. the version you typically get in Linux).