it wont be that easy, they changed secretly other things as well to compensate that
yesterday devs double checked that and marindor confirmed that other "hidden things" are not a bug but rather intended changes
and i am 100% confident by now, fortunately math can not lie
its not mathematically possible that city on the end of the tech tree doesnt even have 1% decrease while in fact it has most expansions placed and cities somewhere in the middle with less expansions has lower difficulty now with bigger impact
most likely what they did is they took city on the end of tech tree, lowered impact of expansions as much as possible while buffing other things (most likely research techs) and made sure it doesnt exceed current difficulty, because then it would be obvious that something fishy is happening
and since there are very few players on the beta on the end tech tree who actually care, this would go unnoticed for quite some time
i just hope some miracle will happen in next chapter so players are willing to progress in tech tree and spend some money so this game can continue