Wolf lowering springs only for diesel?

Hello community! I am looking for lowering possibilities for my Escort MK7 1.6 16V ( 97 year of construction ) and since a complete chassis is quite expensive, I have landed for the time being with lowering springs. Since I found at Ebay of Wolf which for 59€. This seems to me to be a bit cheap, because most other springs cost 100 or more. What is confused me is that in the description is that the springs are only suitable for diesel vehicles. However, can’t imagine what feathers have to do with diesel or gasoline (apart from the weight difference of the engine, which is regulated by the maximum axle load). Greetings and Merry Christmas to everyone!