"The strongest evidence for biologic underpinnings of gender identity"? There's certainly an association, but the phrasing here is basically dishonest, especially given that this is 2014 paper, if it were published in 1967 then you could say that the authors are simply guilty of treating identity as being coterminous with expression.
What this paper clearly suggests is that hormones influence behavioral preferences and that a combination of said preferences and other factors in turn generate an understanding of who one is. The fact that self-understanding plays a significant role in the formation of 'gender identity' is strongly suggested by the fact that telling the subjects that they were genetically male triggered a change in their social identification.
There's basically no direct evidence that hormones are driving identification except through their influence on behavior and even worse than that, the relationship is non-deterministic. In other words, it isn't even correct to say that gender identity is "biologic in nature" for cases where the subjects are literally, hormonally normal, natal males. Hence, it is not accurate or reasonable to say that "the current data suggests a biologic etiology for gender identity" since it is - according to the data - not necessarily relevant.
In general, when making causal statements you need to actually interpret that data to identify the salient drivers: what is sufficient, necessary or at least of primary relevance. You can't just rely of probably causal correlations. To give an example, lower intelligence is strongly predictive of being obese. It is obviously not really accurate to say that "the current data suggests a cognitive etiology for obesity" since not all fat people are unintelligent and that causal association is mediated by societal factors in any case. Moreover, when we talk about obesity we are generally interested in why people are fat now and not say 100 years ago. Hence, intellectual ability may not even be relevant and to suggest it would, in many contexts, be interpreted as a dishonest rhetorical ploy.
The apparent function of their own conclusion can be interpreted in the same way; research on gender identity issues is done primarily to inform treatment and understand social trends. Stating that the cause is "biologic in nature" is then misleading if there are evidently other (modifiable) factors involved.
. So enjoy, i geuss?
