I have highlited some key words you may have missed. The common non proper design on splitters has the cyl bolted to the top of the rail or else close enuf that the cyl body touches it when the beam bows under splitting forces. This binds and bows the rod too, causing scoring and seal problems and predisposing the rod to bending. The rod is also out in the open where it can get dinged. It is no wonder you are called on to replace a lot of these. The problem of improper design remains as the cause of bending.
The cyl inside the beam in 2 way splitters is suspended from just 2 pivot points, as it should be on all splitters. The cocking force on the wedge assembly is greater than the other design because force is applied several inches lower than where the log is. This cocking force is not a factor in rod bending because of the pivots. It just wears more on the guides of the wedge assembly.
larry