We can't say for sure without concrete evidence, but I can understand someone's argument for believing Saudi Arabia funds global jihadist terrorism. Why? Well, much of the oil and resources that organizations like ISIS use reportedly come from Saudi Arabia. These resources help terrorist organizations in the Middle East to purchase the latest weapons and lands and to run their own state.
Therefore, Saudi Arabia can only be called a global sponsor of terrorist if it can be proven that they fund ISAS, which is currently the World's biggest known terrorist organization. We can speculate, but can't officially blame Saudi Arabia without reliable facts.