Watson proved too strong for Benjamin Allatt, David Put, and Sung Min Lee to win the gold.
In the 10-fighter Senior division, Watson defeated Paula Monta in the first round, and then won rematches against Allatt and Min Lee.
He then matched up against with Park in the final, but this time the roles were reversed and he was narrowly beaten.
Father Ross Watson said both Canberra and Sydney had been a good gauge as to his son's ongoing improvement in last 12 months from training in the Netherlands.
There are still things he needs to work on, "but by far, he has more solutions on the mat now than before when competing because of it," said Ross Watson.
Keightley Watson will have no down time since arriving back home, as preparations begin for the Asia-Pacific Championships, being held April 20-22 in the United Emirates at Fujairah, where he will represent New Zealand in the 100kg+ Senior Men's team.