While I'm sure you intended your answer to be helpful, it further muddies the issue, in my opinion.

Here's the way I understand, and handle, the service issue:

On the French side, the service is included in the menu price. Therefore, if the item is $20, you will be charged $20 for that item, and there will not be an additional charge added to the bill for service. Period. If the service was exceptional, then it's appropriate to leave a few dollars in cash. The only exception is if the MENU, not the bill, states that service is not included. In that case, it's up to you to leave what you feel is appropriate for the service.

On the Dutch side, the service is not included in the menu price, however, you will still be charged only $20 for a $20 item. The difference is that many Dutch side restaurants are now adding 15% service charge to the bill. This shows up as an additional item and it's easy to see. Again, you can add more if you feel the service warranted it.