Ok, I looked them up.
The gemara does appear to be setting a standard for goyim, the standard being ??? ??? ?????? ??? ??? ????? ??? ?? ?????? ??? ?? ????? ??? ??? ???? ??? ???.
The rambam brings it, as you noted.
Still, I wonder.
Firstly, it is kind of hard to expect goyish courts to know what to do based on two lines in the gemara, quoted in the rambam, with minimal explanation in the nosei keilim. What sort of evidence must the eid have seen? Are there drishos v’chakiros? etc.
Secondly, the gemara says that when there is a lot of crime, beis din kills people even though they are not chayav misah. (Sanhedrin 47b, Tur CM 2:1). I tend to think there is more violent crime now than there was back then.
Thirdly, the gemara usually speaks about killing people, but the standards of evidence are the same if you want to fine him or beat him. So are the goyish courts not allowed to fine someone without an eid?