There is always something that has to be built first, and we have to remember that its not just the choice you make, the time you build that building impacts the power of new cities.Otherwise you might as well have Settlers cost 65 more production and start the city with a Monument
Take your note above for example. It might seem equivalent at first, but its not even close. The version above would allow a well established city to spend just a little extra and give a new city a massive boost to its start. The early hammers spent on a building for a new city is a big deal, its what moves the new little colony from an absolute waste of space into something starting to hold its own weight.