AMuzi wrote:

Tom has a point in that most linear ("V") brake anchors do
not
have cylindrical heads and actually do look more like an
'internal
wrenching bolt':

Tom misses the substantially more important point that you won't find an "internal wrenching bolt" with metric threading, and that functionally the thing that fixes a V-brake's cable is a metric socket head cap screw. Just as a brake pivot bolt is usually a button head socket cap screw whether its head is domed or conical.