I just looked at a sequence of Olaf the Violin Maker videos on a restoration of a Hill antique violin.  Although unmentioned by Olaf, the violin had a very unique peg spacing in that it appeared that each side of the peg box was equally spaced for 3 pegs, with the middle peg space on each side unused.  I could not extract a useful photo from any of the YouTube videos, but did find something as an example (although not as pronounced as the French made Hill).

The only reason that I can make for doing this is ease of hand positioning for tuning.  Finding the peg hole for the a string must be difficult because of interference from the scroll.