I'm guessing/hoping, from my own experience in metalworking, that the bores are finished at the very least to the equivalent of ANSI/CAMI 2000. That would be a bare minimum, but I suspect at least with the Lapcos and DYEs that the finish is significantly higher than that. There is lots of talk about 'stiff arbor honing', but that tells me only something vague about the method used on the bore, and nothing about its refinement.
And yes, I'd considered a slurry, simply based on volume. But there might also have been final polishing phases with bobs and paste, or the equivalent, at least in the cases of the higher-quality bores.
The wavy finishes may well be indications of something like a short hone or polishing bob improperly controlled. Yuck. It's a nauseating thing to look at, and to think about. Someone did it, someone saw it, and someone signed off on it.
And then someone bought it.
But there surely have to be barrel makers here, or at least those who have been in on the process.