Edited to say there’s another yet inaccurate comment in the post above mine. Nothing in the article suggested that this trans woman wanted to discuss breast size.
I do take your point but given that they were in the bra dept, it's unlikely they were wondering where the scarves are displayed or where the Food Hall might be... Talking about breasts is kind of baked in when you're shopping for bras.
Even if he wasn't talking about those things directly, it's still making women feel uncomfortable and putting them in a difficult position. And overriding the consent of others is a central tenet of paraphilias, of which autogynaephilia is one.