It's been used by long-distance competitive (RAAM -- I think John Moreno might have come up with it) and randonnee cyclists for years. It is one very effective method of combatting Morton's neuroma, or hotfoot because it apparently imposes less pressure on the metatarsals in the ball of the foot, and therefore doesn't interfere with the nerves.

We are talking touring, so the idea of less efficiency for sprinting doesn't come into it. The issue of toe-overlap is a real one, and may end up deciding where the cleat finishes to provide a millimetre of clearance. On some bikes, even with cleats in the forward position, toe overlap remains a problem.

I have been sliding the cleats on all my shoes back as far as they will allow in the slots for years -- since I took up randonneuring and touring with clipless pedals, and after a bad episode on a tour in August 2002.

I am finding the Ultegra SPD cleats on my Shimano "go-fast" shoes don't go back far enough!

Touring cyclists are entirely free to use whatever they want... they don't have to conform with any particular fashion. Almost any kind of shoe with a stiffish sole will do with plain platform pedals, or with clips and straps (which is what I started with about 11 years ago).