I wanted to do a massive double upgrade of all my buildings, more than 20 and most of them were granaries,
with the two mini wonders, Renaissance + Industrial Revolution.
Result : only one of each type of building was upgraded.
I had more than 10 small granaries and only 1 was upgraded to modest.
So, 2 expensive GPs, a GS + GB, were actually wasted.
Maybe very early in the game both mini wonders are usefull for upgrading your palace, otherwise ignore them.
with the two mini wonders, Renaissance + Industrial Revolution.
Result : only one of each type of building was upgraded.
I had more than 10 small granaries and only 1 was upgraded to modest.
So, 2 expensive GPs, a GS + GB, were actually wasted.
Maybe very early in the game both mini wonders are usefull for upgrading your palace, otherwise ignore them.