It's definitely possible to get 9 and 13 to appear together. I ran the following script in neshawk:
local HIT_T = true;
local do_once_temp = true;
local i = 0;
local j = 0;
local k = 0;
local l = 0;
while (HIT_T == true) do
if (do_once_temp) then
savestate.loadslot(1);
do_once_temp = false;
end
i = math.random(0,4);
if (i == 0) then
joypad.setfrommnemonicstr("|..|.......A|");
end
if (i == 1) then
joypad.setfrommnemonicstr("|..|......B.|");
end
if (i == 2) then
joypad.setfrommnemonicstr("|..|....S...|");
end
if (i == 3) then
joypad.setfrommnemonicstr("|..|........|");
end
if (i == 4) then
joypad.setfrommnemonicstr("|..|......BA|");
end
if (emu.framecount() == 800) then
console.write(memory.readbyte(0x0661));
console.write('-');
console.write(memory.readbyte(0x065F));
console.write('\n');
l = l + 1;
savestate.loadslot(1);
end
emu.frameadvance()
end
The starting frame (where savestate 1 is loated) was 536.
This gave me values of 9 and 13 about 1% of the time.
The key seems to be to delay when you press start. Originally I ran the script having already pressed start on the first possible frame and I got 0 results after much longer runs. In the above script, there is only a 1 in 5 chance to hit start on any frame.
As you can see this script didn't save what the inputs actually were, but hopefully this helps a little.