I first noticed this on FreeBSD 13-RC4, but it's still in RC5. This is a very minor issue, but since it seems to be incorrect, I wanted to report it anyway. I noticed that if I press any of the arrow keys at the boot menu, it will drop to the loader prompt just as if I had pressed "3" on the keyboard. If I remember correctly, the previous behavior was that pressing an arrow key would simply stop the boot timer.
^Triage: I'm sorry that this PR did not get addressed in a timely fashion. By now, the version that it was created against is long out of suppoprt. Please re-open if it is still a problem on a supported version.