I’ve revisited the ovo stone costs for additional mining technologies. I have investigated all the technologies that do not cost stone until cupellation and of the additional ones of the ovo only the first one since it only asks for 250 stone, to be practical do not use the second one because it asked for 500 stone, that is why in the image the boxes are empty of mining technologies and the additional ones of the ovo has 2 points because two technologies are missing to investigate (1/3). That gives 75 gold per minute on each villager
A test with another civ with all mining technologies up to cupellation, that gives a little more than 50 gold per minute. The steppe refuge gives you a higher gold rate in third age than other civis in fourth, without any technology they collect 60 gold per minute and with the 3 technologies and 1 of the ovo, 75 gold per minute.
A correction on the wood, it is better to see it in its entirety the mongolian saves 950 wood by not building 19 houses.
I would bet that the steppe shelter and to a lesser extent the kaganto palace is the reason for so much winrate.