I think the grout line size really can depend on how good the tiles are. Did a job recently with Turkish tiles that were so poorly made that my grout line size varied enormously. Took me a while to figure out that on 1 side of the
tile, the edge was more or less square where the other side of the
tile the edge had a distinct angle to it from the mould. As the tiles were not patterned as such, they could be put up either way. This gave rise to the occasions where you were getting 2 tiles adjacent to each other with the angled edge. This made a big grout line. I had to ensure once I realised what was going on, that I fixed the tiles the same way all the time. Using a bigger basic grout line you can lose a lot of these errors more easily.
Grumpy
Grumpy