Pointing out that there are probably scammers in the system is an acceptable statement, IMHO.
Saying you know people scamming and lying is a whole different thing. Now your calling an individual a liar without benefit of medical history or a physician's shingle on your wall. A layman making a highly complicated diagnoses on a spur of the moment, without proof....or thought.
PTS and 'shell shock' are not the same things. Many of the same problems will manifest themselves the same in both, for similar reasons. Causes may be similar. However, PTS has a much more expanded view of things than the simple diagnosis of 'shell shock' from WWI. Medicine has gotten a lot smarter. A person can accumulate PTS and never have a problem. Or they can accumulate it and single incident on deployment can bring it all bubbling up
There's also findings that are showing mefloquine poisioning can mimic PTS and the treatment for either are not the same.
So perhaps that is what the person is really suffering from, quininism, and not PTS. Either way, not having a medical background and knowing the specifics, anyone questioning individuals diagnosis's would do well to mind their own business.