Question: when using a lube plate, doesn't it prevent the pin from come down further in the hitch? Does it affect how well the pin can be wrapped by the hitch mechanism?
Here is the way I look at lube plates. They were invented because folks didn't want to grease the tops of their hitch plates. The grease makes the tops of the plates dirty.
If my hitch manufacturer designed mine for use with a lube plate then it would have been included in my paperwork and I would have been instructed to use it instead of grease.