Should I be taking you seriously ALR?
The reason why is because parts of the Routeing Guide contradict other parts of the Routeing Guide and there are plenty of examples that don't conform to your supposed 'rules'. As there is no black & white 'rule' it is necessary to look at example journeys to see what fits, and to also look at how booking engines interpret routeings....
My 'supposed rules' are written in black and white in the Routeing Guide. They do not contradict any other part of the Routeing Guide that I have seen. I can't comment on these 'examples that don't conform' to the Routeing Guide as you have not stated what they are.
Yorkie has said in other threads how journey planners are not always correct, so saying "my rules" aren't consistent with them is almost laughable, the journey planners are only as good as their programming.
....Your quote itself: "find the permitted routes to London," "find the permitted routes from London," "use a combination of those to make a permitted route from origin to destination." Does that actually specify you have to travel via London? No, it does not....
Erm, yes it does, in the very words you use.
Find the permitted routes to London. That'll be going to London then.
Find the permitted routes from London. That'll be going from London then.
Use a combination of those to make a permitted route to London. Well, this seems to be where you are going wrong.
Having just mentioned getting permitted routes to London and permitted routes from London, do you honestly think "use a combination of those to make a permitted route from origin to destination" really means "forget everything you just looked up and start again with the maps, but don't worry about going via London, it's not really important to be honest", rather than "use a combination of [a permitted route to London that you have just looked up and a permitted route from London that you have just looked up] to make a permitted route from the origin to the destination".
....This example of vagueness isn't a one off occurrence. Your constance ignorance doesn't help, either. There is no right or wrong answer, so calm down and get over it!
There is nothing vague or contradictory here, so I think you should follow your own advice and 'get over it'.
Incidentally, constance ignorance? (I assume you meant constant) What am I being constantly ignorant of?