That seems like a strange restriction to put in place, seeing as how KL/AF/BE codeshare with many other airlines.
It's a great shame and a bit of a wasted opportunity if these routes cannot offer seamless onward connectivity. Not only that but a huge number of non European people who study in Dundee or St Andrews who could potentially have used KLM for onward airside transit to the far East, South America or Africa will now be put off by the idea of having to obtain a costly Schengen visa just for the simple act of having to go landside at AMS to recheck their baggage.