Possible explanation, head cannon stuff..
What if around 2260's there was a refit fleet wide being started? Minor refit between Pike and Kirk enterprise in 2265.
I mean every 5 years or so, ships have to undergo a typical refit. Replace things that have service limits, lets say, the warp naccelles have only, say 2000 light years in there service limit. At that time, they need to be overhauled. So they swap out nacelles every 5 years, and while doing that, swap out any parts that have excided or approch there service limt. ( I remember a voyager episode with them replacing the warp coils..)
So what if, square nacelles are just something that starfleet is trying the refit period? Seeing if they work better long haul? They don't replace the Connie's because they find that there warp coils are just fine, and don't need a complete swap??
We can think up all the head cannon we'd like, but in real world, Fuller wanted square nacelles and flat ships.. But he can't do that to the Connie ( though they did squish it abit) John Eaves is doing some head cannon to, he may not like putting square nacelles on Tos ships, but hey, he's getting paid.. Square nacelles it is!
What if around 2260's there was a refit fleet wide being started? Minor refit between Pike and Kirk enterprise in 2265.
I mean every 5 years or so, ships have to undergo a typical refit. Replace things that have service limits, lets say, the warp naccelles have only, say 2000 light years in there service limit. At that time, they need to be overhauled. So they swap out nacelles every 5 years, and while doing that, swap out any parts that have excided or approch there service limt. ( I remember a voyager episode with them replacing the warp coils..)
So what if, square nacelles are just something that starfleet is trying the refit period? Seeing if they work better long haul? They don't replace the Connie's because they find that there warp coils are just fine, and don't need a complete swap??
We can think up all the head cannon we'd like, but in real world, Fuller wanted square nacelles and flat ships.. But he can't do that to the Connie ( though they did squish it abit) John Eaves is doing some head cannon to, he may not like putting square nacelles on Tos ships, but hey, he's getting paid.. Square nacelles it is!