I was always under the assumption it was the honouring of the alliance with France which was the tipping point, which all stems from the Second Boar war. From 1900 to 1914 it is certainly possible to see a less aggravating Germany and a more annoying France.
Well, they actually were, no creative word-bending needed, obliged to go to war in the case of violations of Belgian neutrality, whereas they weren't under such obligations to France. Thus, without Belgium, they still need to find an excuse to enter the war, even with their relation with France being the same up to that point. Not that they can't find such an excuse, but that won't come at once.
Still, most likely, needs
more to keep Britain neutral (such as the changed situation after the Second Boer War you posit), but if you want to keep the Brits neutral, keeping Germany from violating Belgian neutrality is probably a necessity.