Is distinguishing trans-women as trans-women problematic/transphobic?

C.
I was scrolling through Twitter a few minutes ago and saw a video of Chimamanda Ngozi Adichie speaking her opinion that trans-women are trans-women, their experiences in life start from a place of "male privledge" and how she believes that trans-women issues shouldn't be combined as one with womens issues. 
Obviously people are upset or saying that her words are transphobic and problematic, but are they really? I can say that as a black woman I have certain experiences that I go through that are completely separate from women of other races/ethnicities. Does acknowledging that take away from either of our womenhood? Does acknowledging that difference make any of us less of a woman? Of course not. 
So then why is it wrong to distinguish the difference of experiences between trans-women and cis-women? Why is pointing out that difference transphobic or "taking away" from trans-women or marking them as "less than a woman"? 
 (You can watch the video here: bit.ly/2mv6p8X) 
Update: A lot of women here either understand intersectional feminism or they feel that saying trans-women are trans-women is taking away from their womanhood. I personally didn't understand the opinion to be that way. If we can look at two women one white and one poc, and understand that although they have a difference in experiences they both are still women, why can't we do that for trans and cis women? Women in general share the same issues but the way those things play out is influenced by the type of women you are I.e. Race/class/gender/religion/illnesses etc etc. None of these things makes us less of a woman in my book. There's no cardinal rule to womenhood..and I guess understanding that diminishes the hurtful thinking that transwomen aren't women if people say their issues don't have to be combined with ciswomen issues.