Trans-identified is an ideological reference to trans individuals based on a desire to avoid referring to trans men as men and trans women as women.
In Gender Critical parlance, trans men are TIFs (trans-identified females) and trans women are TIMs (trans-identified males). Both of these terms are intended to emphasise that trans people are not their acquired gender and just “happen” to sound like male and female names.
Superficially it is often argued that it is “a clearer way” of describing trans individuals. However, the use of this terminology is ideologically driven by the need to ensure that trans men are never referred to as men, and trans women are never referred to as women.
In Gender Critical thought, the act of identifying as something is artificial and driven by choice, rather than reality and deeply-held affinity. Thus, referring to trans people as trans-identified is to frame being trans as something people can identify in and out of, indicating it is in someway superficial and can be changed. For example, it is the difference between saying someone “is a journalist” or saying someone “identifies as a journalist”.