sourdough,
I think along the same thought process as you.
My understanding comes from and is based on the "old bias ply numerical truck tire load rating/inflation charts", back when we used to weigh each axle and adjust PSI to the actual load that was on the tire. So, yes, the heavier construction of the LRE tire would be more robust, built heavier (it even weighs several pounds more than the LRD tire in the same size) and it would be sturdier, but the actual "certified rating" would be the same at lower pressures. In other words, even though it's a "beefier tire" it hasn't been subjected to testing to specifically rate it (certify it) to be "better than" the D series tire at the same PSI. So to "shortcut" the process the load chart for LRB, LRC, LRD and LRE are all "combined" for a specific tire size, and as the pressure/ply rating increases, so does the load rating, up to the highest PSI rating which is "last certification for that specific ply rating".
What goes up, also goes down, so a LRE is also "rated to carry the load" of an LRD, LRC and LRB tire of the same size at the load ratings those tires are certified to carry when inflated at the PSI for that lower load rating. It would seem (at least to me) that the LRE tire "ought to carry more weight" at 65 PSI than the LRD at that pressure because it's a more robust tire, but it's not "certified or tested" to carry more, so it's "rated" the same at that pressure...
The same applies to a LRC tire at LRB pressure, a LRD tire at LRC or LRB pressure....
Now I think I've even confused myself
