Usually AI has huge yields when it has many settlements. Could you check them? And it's more common for more aggressive leaders, who conquer settlements from others, of course.
Went back and checked a couple of older saves, and Napoleon (Emperor) in at least two games also had oversized yields, and in both cases also was leading or near-leading in number of settlements (luckily, he wasn't anywhere near me in either game!). In my latest game, I noticed that he went to war with his nearest neighbor before they were 30 turns into the Antiquity Age, so he starts early.
On the other hand, neither he nor any other AI Leader/Civ that I've encountered makes good use of their massive leads to compete to win the game. Except for hoovering up every Wonder they can grab in Antiquity, I do not find the AI to actually chase any Legacy paths/Victory conditions competitively:
Their Distant Lands settlements in Exploration re nowhere near any Treasure Resources - in fact, they will plop down a settlement that is 1 - 2 tiles out of reach of a Treasure resources, to no purpose that I can fathom.
In Modern Age, they start out strong with Explorers, then seem to lose interest so that the game ends with them having 4 - 6 Relics while I have 12 - 15.
I have never seen any AI complete the Modern economic path with railroads and factories, or even come close, despite frequently having piles of Science and Gold with which to do so.
The only consistent 'winning/competitive behavior' I have seen from the AI is in war. They can and do buy or build 1 - 5 units per turn for as long as they can - not using them very efficiently, but throwing up a mass of roadblocks and 'Unit Waves' that drag out the wars to mutual exhaustion. - And mutual exhaustion means that sooner or later an AI opponent will offer a settlement in a peace deal, which is probably how Napoleon gets so big so consistently - he thrives on negative relationships, and negative relationships come from and lead to war as nearly continously as you like.