As a member of the DLC member states are required to report ticket convictions received by a motorist back to the state where they are licensed to drive. Their own state then determines if this offense will be placed on their driving record and if any points will be assessed.
PA is part of the DLC, but if you pay the out of state citation, than PA does not issue points on your PA license. It has been that way for many years, but according to the above article, it may change in the future.
It sounds like you got something else going on, that you got the letters + the 16 mph over might be a big thing in that state (like 30+mph over in PA is auto suspension of your license). Doesn’t mean you are getting PA points.