It's about half and half, 50x comes from the language and 50x comes from experience. The important part is to add those factors together by good management.
The math here doesn't really make sense, factors multiply, so if there were two 50x factors the total improvement would be 2500x. In other words if one factor is 50x, the other one must be 2x to get 100x total.
This is useless pedantry. You know what they were trying to say: The improvement can be attributed equally to using a more suitable technology and to better knowledge of the problem domain.