There are some studies that investigated childhood trauma in patients with Depersonalization Disorder:
Overall patients tended to be a bit more likely to have endured childhood trauma, but no type of childhood trauma emerged consistently as specific to Depersonalization Disorder.
The same was true in some studies about secondary depersonalization:
In the first study no difference was found between patients with panic disorder wit secondary depersonalization and without. The same in the study about PTSD.
Even if these studies found a clear association of childhood trauma with Depersonalization Disorder, this wouldn't be enought. These studies are cross-sectional, so they cannot prove that childhood trauma causes Depersonalization Disorder.
You might also add this study to your collection:
It shows, just like all other studies that investigated comobidity of Depersonalization Disorder and also included PTSD, that only a very low proportion of sufferers also have PTSD (in this study 3.4% lifetime and 1.7% currently).
What is known is that traumatic events can cause transient depersonalization. But there is no evidence that traumatic events trigger Depersonalization Disorder. Simeons case series found that 25% said that severe stress precipitated Depersonalization Disorder, but severe stress is not equal to a trauma.
All in all there is no evidence that Depersonalization Disorder can be regarded as a trauma-based disorder, but evidence for the contrary exists.
It would be even better if there is evidence that it doesn't have to be caused by anxiety or drugs either.
In Simeons case series the disorder was triggered by drugs only in a minority. 13% had taken cannabis, 6% hallucinogens, 2% MDMA and 1% Ketamine. You can't add these numbers up, because participants were seemingly allowed in this study to mention multiple triggers.
Panic attacks were a trigger for 12%. In 49% there was no trigger for Depersonalization Disorder.