That's not what he says. It says that they tried to keep the trunks. So they played around with the design and ultimately came to the conclusion to lose the trunks.
“The costume was a big deal for me, and we played around for a long time,” Snyder says. “I tried like crazy to keep the red briefs on him. Everyone else said, ‘You can’t have the briefs on him.’ I looked at probably 1,500 versions of the costumes with the briefs on."