There was that transman in the news who stopped having periods when taking testosterone drugs but then wanted to have a baby so stopped the drugs, got periods back, got pregnant, had the baby, then went back onto testosterone drugs, stopped having periods again and called themselves the baby's father. Or at least wanted to. I believe the courts wouldn't allow it.
So yes, periods can definitely be very much part of a transman's life because being a woman is not about what you wear, what name you use, how you 'perform' or how you style your hair.
The one thing that all women share, throughout history, across cultures and all around the world are the experiences surrounding their reproductive organs.
And men cannot share that even if they have implants, surgery, drugs and body parts added or removed. They still won't share the one common experience of being a woman which is what makes us women. They are a different kind of man and should have all the rights and protections they need to live a safe and fair life.
But they should not claim to be women because they can't ever be.
Transwomen are different to women. That should not be a bold statement, it should not be controversial and it should not cause people to lose their jobs and receive death threats.