Like Rachel Dolezal, this seems to have some correlation with a history of child abuse. Something about being a victim and feeling the need to identify with a heavily victimized group, I suppose?
I don't know what those histories are, or if that is the common trend. However, if that's the case: It could possibly be a coping mechanism to deal with the poor self esteem that comes from their self identity as a victim.
If you get no sympathy, attention, or increased self value from your status as one type of victim, perhaps you can identify as another type of victim to increase your sense of social standing and self worth.
In fact, some classes of victim get so much special attention that it results in tangible perks being bestowed on them from society.
It reminds me of hearing about not long after 9/11 of a story of someone who had lost their parent due to a more common cause go around claiming they had lost their parent in the 9/11 attacks.
For whatever reason, they wanted the attention that they knew they would get from people if they connected their loss with an event that would elicit a response from people.
Of course, you don't need to be a victim to want to self identify as a social category you think will get your more attention, respect, sympathy, or whatever.
People have no trouble lying about who they are for attention in a lot of ways.
Given that blacks generally are not an abused of mistreated group in this country anymore, but they get all kinds of special attention, sympathy, or even tangible perks in some cases, there's little to no downside to self identifying as a group that is likely to get you more attention than you think you'd get being white or Jewish.
It's probably not unlike Elizabeth Warren self identifying as Native American for college money and political expediency. There was no downside to identifying that way. They aren't an oppressed people group anymore. They are welcome into society like anyone else. But the benefits that come along with that invented identity gave her the potential to cash in on some special perks and extra attention she otherwise wouldn't have had.