So this is the modern antifa flag used here, it is the red socialist flag overlayed by the black anarchist flag, it is directly based on and referencing this flag Which was the flag of the militant wing of the German Communist party.

I suppose you could say in the original post without the color it becomes more generalist in meaning but I suspect it was just for visual design and not to signal anything more anarchist and less socialist.

Regardless, trans rights should not be synonymous with antifa even if we are allies. The oligarchs are trying very hard to say that trans people are all "radical Marxists" let's not make it easy for them. We are people just like them, and it isn't Marxists vs capitalists, it is "we the people" vs "the ruling class of super rich" who want to control our lives and take our freedoms before giving up their domination and it always has been.

Tldr, that flag is antifas, antifa is much easier to villainize than "the trans population". Antifa is a political direct action group which I support and many do, but many don't, either because antifa has generally been anti-capitalist and some people really like capitalism (including many trans people) or simply because they just associate antifa with trashing downtowns and rioting and it's easy to be against those things. It's an easy target. Don't make trans people an easier target by lumping together trans rights and antifa as being just the same people.