Why do people think they spoke to Shrier? I suppose I feel the natural approach would be to find someone who has been historically friendlier, more of an ally.
Anderson has previously spoken to other "non-allies" critically, like Andrew Sullivan and Jesse Singal. This is only new ground for Bowers.
I'd say it's partly because Shrier is open-minded and would listen, and willing to bear the flak of those not liking what they're saying. Would an "ally" be prepared to publish a "transphobic" piece?
The New York Times rejected Anderson, as the piece says. They presumably didn't want the flak. (And it's Bari Weiss publishing Shrier, not any real outlet).
I also wonder if there's a deliberate attempt to reduce the "partisanship" of the debate. They possibly agree to some extent with "Irreversible Damage" and want to help publicise Shrier's work.
Note that at least Bowers' speciality is male genital reconstruction. Both the entire field being discredited due to female ROGD+detransition, and young males getting puberty blocked, potentially interfere with that work...