"I didn't really understand why people were cancelling their plans to hang out with me.
"Next minute Kate comes around the corner. As soon as I saw her with a TV camera I knew what she was going to say."
McGrath lost his legs four years ago when he stepped on a landmine while serving as an Australian Army combat engineer in Afghanistan.
As he was being airlifted to safety, the then 24-year-old made a vow to the men who helped save his life that they would see him see him represent his country again, not on the battlefield, but in the Paralympics.
In Rio the reigning world para-canoe champion made good on that promise, but said he was genuinely shocked to receive this second honour.
"I thought there was definitely people more deserving than me," he said.
"I hope to carry that flag high."
The Kiwi-born athlete said he feels lucky to be connected to both countries across the ditch.
"It does pull on the heartstrings when you want to barrack for the All Blacks, and you're out here in the green and gold," he said.
"(But) I see Australia and New Zealand as a family. On the 25th of April we commemorate the adversity that the guys from Gallipoli had to go through and it's a celebration of our two great nations."