The one that reads ...
4. Changes Requested by a Passenger
(a) Except as otherwise provided for in the Fare conditions, the Passenger cannot change any aspect of his itinerary (for example the Place of Departure, a Stopover or the Place of Destination as mentioned in the Ticket). In the event that the applicable Fare conditions allow a change of the itinerary the fare will be recalculated and the Passenger will then have the possibility of accepting the new fare or keeping the original Carriage as shown on the Ticket.
Meaning that the airline might allow you to change the origin point (for example by substituting London with Amsterdam as the point of departure) but it does it insists that you pay the fare from Amsterdam.
This isn't EU law, this is contract law. One party cannot (with or without the knowledge of the other party) change a core term without the other parties agreement. They have sold you transportation from London to KUL and you cannot substitute transport from Amsterdam to KUL without their agreement. And you have agreed this provision when you bought the ticket.
Now, what would the consequences be of the ECJ or national supreme court deciding that these provisions are indeed 'unfair', or 'illegal'? Do you really think KLM will continue to offer transport from London at a price lower than what they believe they can sell transport from Amsterdam for? Rather than accept that any 'sneaky' Amsterdam origin passenger can get a fare lower than what KLM is prepared to sell it for - they simply will withdraw from the LON-KUL market. Result - same fare at Amsterdam, less competition at London. I'm not going to stretch it further but it isn't unreasonable to assume that KLM withdrawing from the LON market will result in higher prices from LON itself.
So what about if it is special circumstance that causes a passenger to change his origin point? Well KLM's next paragraph seems to be more than fare (pun intended)
If a Passenger has to change his/her Ticket due to a reason that constitutes Force Majeure, the Passenger must, as soon as possible, inform the Carrier thereof who shall then use reasonable efforts to ensure Carriage to the next Stopover or to the Passenger’s destination, without any change in fare.
So if you can prove your 'special circumstance' you can do it, but you got to tell them - you just can't do it without their knowledge, and agreement.
For your information the UK Office of Fair Trading looked at these rules some years ago and decided that they were not 'unfair'. (To be accurate they did say that the rules in effect at that time were badly written, following which better clearer language was drafted - and this is the language that KLM appears to have put into their own conditions of carriage.)