Because the Catholic archbishops’ zuchettos are amaranth; not black.
The color of the zucchetto in Catholicism denotes the wearer’s rank:
the pope’s and pope emeritus’ zucchetto is white;
those worn by cardinals are scarlet;
those of archbishops, bishops, territorial abbots and territorial prelates are amaranth;
and regular abbots, priests and deacons wear a black zucchetto.
You believe the archbishop is making an interfaith statement?
(You would know better than I, for sure!)
Just seems weird.