What Martin seems to be saying is that the ENTIRE ride now would fall under the DIYxGPS Mandatory route rules
No, what Martin was saying was that if you entered a calendar event that was 215km by the routesheet, and relying upon that, only topped it up with an 85km ECE, then if you took a shortcut or two (by mistake or being forced to due to a road closure, etc) on the calendar event then there is a risk that when you submit your final GPX tracklog he'll find the entire thing you rode was under 300km and so he wouldn't validate the ECE part.
This makes sense. You shouldn't be able to claim 3 AUK points unless you've ridden at least 300km. I don't think anyone will disagree with that. (You'd still get the 2 points from the completed calendar event though.)
What this means is that it is the riders responsibility to ensure that they complete the full distance. If the calendar ride is advertised at 215km then you have a few choices:-
a) Risk it, don't do any checking yourself and only add an 85km ECE leg
b) Risk it, don't do any checking yourself, but add an extra 10km onto the ECE leg just in case
c) Plot the route of the calendar event in a mapping tool and find it is only 209km, so make the ECE leg at least 91km.
d) Plot the route of the calendar event in a mapping tool and find it is only 209km, so make the ECE leg at least 100km just in case you go wrong on the calendar event and shortcut something.
e) ...etc...
Martin can't check each and every calendar event so it must be down to the rider themselves.
On the day it may not even be down to a shortcut
* GPSes don't do cumulative distance very accurately
* You may forget to (re)start the GPS after a control
* Loss of signal due to tree cover may rob you of a vital 500m
* Batteries can go flat leaving you with a missing section of tracklog until you notice, or it can turn itself off on a rough descent, etc
In the absence of your own checking then relying on anything other than the nominal distance of the calendar event increases the risk of non-validation of the ECE part.
Even relying on the nominal distance can be risky in some cases, there are some calendar events right on the edge and some GPSes may log the ride with a tracklog distance under the nominal distance.