I don't see it as much different than your playing for maximum score. You could win sooner and with less work, but you keep going to get a bigger number because you can.
The game has score as acknowledged at the end of every game. Number of shields per turn in a city isn't acknowledged once a game ends. Maximum score concerns the result at the end of a game. Since number of shields works out
per turn it has no relevance when zero turns remain.
Most of the time when playing for high score or
near maximum score, there exist all sorts of choices about how to expand the empire or focus on the happiness and contentedness of citizens. A heavy focus on the happiness of citizens does not strike me as all that similar to a heavy focus on how much shields citizens produce. Also, playing for high score involves trying to find high value city spots which have a large number of citizens working tiles while also having less tiles that count towards the domination limit (sea squares don't count). The AIs also need controlled to not win, but that has no relevance to highly productive cities. Playing for high score also involves maximizing population within cities at good spots, while also getting in the infrastructure to support the happiness and contentedness of citizens. Each type of specialist can be useful in such histographic games, unlike many other games where entertainers do not seem useful at all. Entertainers do not have any relevance to a city which produces a lot of shields.
Perhaps if maximizing population of cities were the only goal for high score histographic games, they would end up similar. Irrigation might get thought of as the inverse of mining, I suppose.
But, for example, have a look at a city named
Whale Saltpeter. It's on a hill. Planting cities on hills doesn't make sense if trying to maximize shields. I would expect that many people would believe that a city like Whale Saltpeter as optimal as unexpected by many people. That signifies something different to me. Cities sometimes also optimally end up placed on top of food bonus tiles, including grassland cow tiles (because of greater sea squares if the city goes on top of the cow). Cities like whale saltpeter also take a lot of turns to get up to speed. They need workers from other cities to grow more quickly, gold for infrastructure. Perhaps that strikes you as similar to getting a highly productive city up to speed, as one might do in a 20k game. But, then also a city like Whale Saltpeter also needs heavy use of the luxury slider. The luxury slider isn't needed for highly productive cities. The gold needs to come from the tax slider.
Needing to use both the tax sliders and luxury sliders and some form of science isn't like needing to use the science slider.
Also, again, for maximum score a large usage of
sea squares comes as desired. But, for highly productive cities one wants large usage of land tiles. Sea tiles are not like land tiles! Only at the low level of code, I suppose, are those tiles "not much different".
Edit: Playing for maximum score ALSO can involve getting something from AIs, even at Chieftain. War happiness. I suppose getting gold or technologies researched could have relevance for getting a city up to a high number of shields. But, war happiness has use from some point until the end of the game in a high score histographic game (2 of the highest scoring games on record have 4 AIs supplying war happiness). I don't see how things are similar when the AI becomes irrelevant as with a big number city focus in comparison to when war happiness has relevance.
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