France 1940 Allied Strategy

I have played a couple of wargames now playing as the allies to see if I can stop the German blitzkrieg through the Low Countries and France in the summer of 1940. In both cases I found that it was fairly easy to prevent the Germans from steamrolling through.

The basic strategy for success is to not follow the allied Dyle plan and flood the BEF and best French troops into Belgium to defend their frontier. That strategy as in real life makes the attack through the Ardennes a lot more effective for the Germans.

Instead playing the France 1940 scenario in TOAW and also Commander Europe at War: Grand Strategy, I hold the best defensive positions and hold the Germans back. Sure they do some damage to my forces and take some territory, but they never break through or encircle my armies.

The Germans actually started their invasion in CEAW above in November 1939 - so I've been holding them for over half a year already in this exam

So what is happening here? Is there something that these games are not simulating about the German attack? Perhaps the Germans should be stronger and the Allies weaker? Or simply was the Allied strategy badly flawed. In which case the German blitzkrieg can be countered easily by a solid well maintained and supported defence?

One thing I realized though is that in both games I was using hindsight - I effectively followed the same defensive line as the Dyle plan - but I made sure the Ardennes region was well defended so that I couldn't be outflanked by the Germans.

In both games the Western Front ends up looking more like late 1914 than summer 1940.