"It encapsulates a whole [period] of hard work on her behalf."
He said his wife, Sue, had gone over to the Netherlands to support their daughter.
Harry said he was confident Julia and McKenzie could win the A-final, despite finishing second in their semifinal earlier in the week.
"We thought she was in with a chance, they got out early and I thought they were just brilliant."
The New Zealand pairing won gold two seconds ahead of Canada and five seconds ahead of China.
They also managed to shave nearly 20 seconds off their semifinal time, where they had finished second behind South Africa.
The impressive final victory was done in a world best time of 6min 48.56sec, breaking Edward's own world record set in 2012 with Louise Ayling.
Edward and MacKenzie are a new pairing in the New Zealand lightweight boat, with young talent MacKenzie replacing Lucy Strack for the world champs this year. Remarkably, the champion pairing have only been training together for the last five weeks.
Harry said it was "bloody amazing" for the pair to win a world title after training together for such a short time, and he was proud of them both.
The pair have a really bright future ahead, with the Olympics only two years away. Julia and her mum will spend a week in France before coming back to Rotorua.
The victory caps off a remarkable year for Edward.
Edward had originally been named alongside former rowing partner Strack to contest the 2014 international season. But Strack pulled out of the doubles boat, which resulted in Edward racing the single scull events at the world cups.
She won gold in Switzerland and France before teaming up with new doubles partner MacKenzie for the world champs.