BG was bundled up. Temps weren't freezing that day.
Most exhibitionists aren't interested in performing their version of the dance of the 7 veils and wearing layer upon layer of clothing.
That, combined with the fact that he looks to be concealing a plethora of items underneath that jacket he's wearing, items which in all likelihood constituted his murder kit, does not support the theory that his primary aim that day was to expose himself to anyone.
BG is all about concealing himself, not exhibiting himself.
I agree with
@MassGuy. I don't think this was about exhibitionism.
It wasn't about BG wanting to expose his genitalia.
I think what BG whipped out and showed those girls was a weapon.
That's what he wanted them to see up on that bridge.
That would make most young girls freeze.
Heck, it would make most grown women freeze.
JMO.