I don't agree. The Netherlands and Belgium were invaded because it gave Germany a strategic advantage in the attack on non-neutral France.Why wouldn't Germany attack it? Denmark, the Netherlands, Luxembourg, and Belgium were neutral.
I think one needs to provide a more positive reason for Germany not to invade France than French neutrality, one that has to overcome Hitler's personal antipathy to a country that beat Germany*, took Alsace-Lorraine, and forced a humiliating treaty on Germany. And don't forget all that loot: France was rich.
In the unlikely event of a neutral or even a pro-German France, I seriously doubt if Germany would have attacked any of these countries. After all, what Hitler really wanted was "lebensraum" in the east.