After watching this video a few assumptions can be made..Ford did not line bore assemblies,you are correct.Ford held a strict tolerance through out the process negating the need for line boring the assembly.They basically assembled them and 'spun them in' using an electric motor on a stand,spun them till the engines resistance fell into spec. The honing and cylinder process is covered by the video as well.
https://www.youtube.com/watch?v=Xa0PAg7FfMk
Here another photo of Ford spinning engines to a prescribed resistance..the shear size of the Rouge operation is fascinating.