I know that in Italy, double sword is a very unique form of fighting. The trouble is one had to be
very adept and an advanced fighter to use it instead of a shield. Thus it was not very widespread and only expert swordsmen could employ such techniques. I have actually seen it in action at an SCA event years ago, and it looked almost identical to FMA Sinawali! I was very impressed. He was fighting against a shield holder and won!

He was the only one who used it and was quite advanced in his training.