A lot of this hinges on what lens you view race from. I know most people would love to say that we're in a "post racial" society, that race doesn't matter, that being "colorblind" or "raceless" is the optimal view, but given the history of this country, that's just fantasy thinking. There were racial covenants in housing that specifically singled out black people to NOT live in, or much less, even rent housing properties here. That is a VERY specific systemic injustice we can't hand wave away with wishful thinking.
We have to ask the what, why, and who questions. Why is the concept of transracial identity being valid good? Who stands to benefit from legitimizing it, and who will be harmed? At what costs will society pay for such recognition? I think the depths of this conversation go deeper than what this space can accommodate.