Playing on words, the term PTSD, no... all the components of PTSD, yes, they can be inherited through genetics. So yes, TECHNICALLY, you are correct when relating to hierarchy.
There are actual people who would meet the criteria for PTSD with symptoms, but not be able to have the diagnosis based on they are missing the abnormally traumatic event. Saying that though... psychologists, counsellors and such, with backyard diagnosis, are fitting those people into it any way they can.
Genetics are tricky... as even anxiety can cross into a behaviour, which can be changed, yet also be genetic. Like chewing nails is a sign of anxiety, yet a person with no anxiety at all may chew their nails through behaviour. One event in their life, suddenly they have PTSD because genetically they are susceptible to anxiety and other symptoms of PTSD... even though the event itself didn't cause those symptoms, genetically they had them already, or a majority.
Tricky subject actually with the way PTSD is evolving in the DSM... especially when you now have cases coming forward being diagnosed with PTSD, with statements such that their mother was raped when they were in the womb, and they now have tissue memories triggering nightmares and such... and such people have been diagnosed with PTSD, even though I personally completely disagree with that, though psychiatrists have done that under a few cases I've read, as they technically did endure the trauma, but they inherited the memories from the mother to baby and stored them.
Again though, I don't believe such a diagnosis should be given to such cases, as they could have been coerced by the parent, transference from the parent who has PTSD and raised the child from birth with PTSD.... that is by definition a classic case of PTSD by genetics. From the womb, continued through transference of the paternal relationship, then into a PTSD diagnosis... yet having the memories of the mother being raped when they were in the womb!
Weird and wonderful stuff going on with diagnoses. Again though... I don't agree with this information, but I have read such cases.
With PTSD shifting out to a trauma category... I would say, "Watch This Space!" Things will get interesting with the mental health business of diagnosing.