Its related with growth factor, check in difficult handicap table, its only affect AI not human, the problem is simple the ai despite have money cant raise new stack of army, thanks for never ending population consumed building and other stuff. give them proper population per turn will ensure they functional like normal faction. 100 % represent 2 growth population every turn, so now they have 4 growth per turn i think, which is sufficient.
There is no negative side effect from having to many population for AI, for Human its just ruin the immersion, that why you should dont reverse it to human enabled.Happy tweaking Sir Almas 1985