I am watching how this issue develops as Australia is just starting a similar process of route validation. Our routes are compulsory but according to our agreement with the ACP, checkpoint locations should prevent shortcutting, the worst of all possible situations. Virtually all of our 200(+) brevets are BRM, so no extra time is allowed for over-distance routes. We've just initiated permanents in Australia, so this routing issue is becoming more of a problem.
I think the means of validating the minimum distance needs to be robust too; for example; if I run my event (not one so far highlighted as requiring more than 5 controls I should add) through either Autoroute or viamichelin it comes up consistently with a footpath; (a muddy one at that, not even a bridleway) which happens to connect a very lumpy and not very well surfaced lane to a humped and very private road- a footpath ie not rideable along- which eventually connects back up to the normal route having cut out about 3km of nicely surfaced and gently graded; not to mention lovely to ride route of the official ride, for which under the new rules I'd be obliged to add an extra info on the proper route 4km before the lunchtime control just to deter those adventurous riders whose GPS just happened to know this little detour.
A number of regions in Australia have many dirt roads but few asphalt roads. Many times, the shortest distance according to Google Maps or other mapping programs is via dirt roads or even roads that have never been been constructed and never will be constructed (literally through a farmer's plowed field). Pragmatically we are pretending that dirt roads don't exist (generally
).
We are still coming to terms with consistency between the various regions. Some allow routes with small loops and no intermediate controls (rather dubious IMHO), some are 'hardline' shortest distance.
Interestingly, this year some of our brevets are UAF-style 'Audax 22.5' brevets (aka Euraudax) and the organiser can tie the route completely up in knots, if desired, as the riding style prevents shortcutting.