This has nothing to do with PTSD.
A vet that has been ruled incompetent to manage his own affairs is what the OP is talking about. This is a vet who, for whatever reason, has a poerson cvlose to him, usually a spouse or sibling if no spouse is available, assigned to manage the vet's financial affairs. They aqre judged incompetent to manage their own affairs by competent medical authority and only after lengthy investigation will the VA assigned a fiduciary. Even then, they also assigned a VA fireld investigator to frequently check on the vet and audit his/her financial affairs to ensure that the vet is not being ripped off by the fiducuary.
This is a medical determination that rates the vet incompetent to manage his own affairs which makes it a mental health issue and that is why it is included in the NICS database.
I am a retired VA Rating Specialist and had to frequently make those determinations.
In the past, many vets elected to do this so their spouse could have control of the money and the VA did not warn them of the consequences. But for the last several years, the vet is in formed and has to sign a statement confirming his understanding of what may be the consequences of having a fiduciary assigned.
A person legally appointed and authorized to hold assets in trust for another person. The fiduciary manages the assets for the benefit of the other person rather than for his or her own profit.