Of course, this is just a concept and design could be vastly improved on, especially regarding reinforcements that may be needed when the forces become really large. Theoretically, it could work with only one of these two hoses as well if the power is needed only in one direction, but is much more reliable and easier to control when their both ports are in use.
Unfortunately, due to the friction within the cylinders, the target piston is not nearly as precise as the input set by the linear actuator. However, its primary task is to transfer serious force, rather than do it extremely precisely. Due to an enormous gearing ratio of the linear actuator, its input torque is easily handled by almost any Lego motor. Just keep in mind that the total stroke length of the linear actuator exceeds that of a pneumatic cylinder, therefore (at least in this configuration) it can't be retracted completely.
Of course, the concept of cross-connected pneumatic cylinders that follow each other's motion can be practically applied in various other ways, however they must be driven "externally" ― that is, introducing a pump with a T-connector would not work as there is no output for the compressed air to escape from the system!