The man Melbourne won on judges' scores of 115-113 and 116-112 with the third judge scoring a 114-114 draw in the showdown at Stockton, California.
Moloney improved to 26-2, suffering his only losses in his two prior world title bouts, falling to Puerto Rico's Emmanuel Rodriguez in 2018 and Japan's Naoya Inoue in 2020.
Astrolabio fell to 18-4.
Also on the card, WBO middleweight champion Janibek Alimkhanuly (30) of Kazakhstan knocked out Canada's Steven Butler (27) at 2:35 of the second round to defend his crown for the first time.
After stunning the challenger with a left uppercut, Alimkhanuly pummelled Butler again and again with lefts, dropping him to the canvas three times before referee Jack Reiss stopped the onslaught.
The European standout called out all rivals for future bouts, notably rival 160-pouns champion Jermall Charlo, an unbeaten American who owns the World Boxing Council crown, and Mexico's Saul "Canelo" Alvarez, the undisputed super middleweight champion.
"Champions and boxing superstars, where are you?" Alimkhanuly said. "I'm the most avoided fighter. I'm the middleweight king.
"Canelo and Charlo, I'm coming. I'm ready for anybody anytime anywhere."
Unbeaten southpaw Alimkhanuly, 14-0 with nine knockouts, turned 30 last month. He was a 2013 world amateur middleweight champion and 2014 Asian Games middleweight champion.
Butler fell to 32-3 with one drawn.