Well, here's hoping he is correct.
I would bet big odds against it though. Number one reason is that's not the way we see that expansion valve fail. To account for those pressures the expansion valve would have to allow a tremendous flow. I'm not sure the block type valve can do that. I can tell you that the last ten that I prayed were (that), weren't.
Unfortunately the more likely problem is the worse problem that system can endure. It sounds more like the pressures of a compressor running in the throughs of the "Black Death".
Try a valve as they are cheap. I would not do anything else until that diagnosis is complete. It other words, no flushes, no driers, etc. Plug in a new valve, examine the insides for contamination, see if the pressures are good and then do further maintenance if the diagnosis proves correct.
Bosch Master, ASE Master, L1
33 years MB technician