Initially they said trans was a prefix and used it as a prefix, as the original Latin (which they kept telling us was accurate - it meant the 'other side of', and is used in chemistry, though I'm not a chemist, and can't recall its function in chemistry). Trans identified people described themselves as "transwomen" and "transmen" (note - a single word).
Lately there has been a distinct shift way from "transwoman/transman" to "trans woman/ trans man" - it is being employed now as an adjective. That subtle space which has crept between the two parts of the word has been introduced deliberately.
If "trans" becomes an adjective, then it describes a type of woman, in the way tall, or blonde, or slim, or black describes a type of woman. The implication is that these are real women - biologically female - and that only a bigot would treat them any differently from other women.
There is now great insistence on this space - suddenly "trans" is no longer a prefix, modifying the word (which is in some ways accurate - eg, happy/ unhappy; sane/insane etc, where the prefix actually indicates the opposite to the root word); using it as an adjective means that it now describes the word.
This might look nothing, but it is a huge linguistic leap.
Language does change as we all know - but natural linguistic changes come gradually over centuries with common consent to the change; they aren't pushed on a reluctant population in the space of a few years.