I wouldn't be surprised. There's always an exception, but it's highly unusual for someone who hasn't played much in their younger years to be that good in their golden years.
This conversation has caused me to think of a good man who I played golf with on numerous occasions over the years, his name was Enos. We called him "Eenie." I didn't know him until I started playing with his son-in-law about 16 years ago. We became good friends, and over the course of the following 15 years or so - he would invite Eenie along to join us. When I first met him, he was around 75-yrs-old. He was a small guy, very wiry build, but he was in great shape and flexible as a garden hose. He refused to play the senior tees, lol... he would have none of that discussion, he was stubborn for sure. But at the same time - he didn't exactly need to because of his driving. He was still popping them out there around 230-240 yards. He'd always say, "if I move up to the seniors - I lose 3 strokes off my handicap and the holes don't get any bigger. I'll stay here with you guys and keep my strokes."
Naturally over the course of the next 10 years or so, he lost considerable distance and was basically left with no other option but to swallow his pride and move on up. He shot his age a few times, but always lamented that he would still shoot even par if he could putt half as well as I did. A couple years ago we played quite a bit together, and on several occasions he would talk about how many friends of his was dying off. I would always say something along the lines of, "Eenie - you're gonna live to be a hundred." He would always chuckle and say, "God, I hope not. 70 years of putting up with the same woman, I'm not sure I could take another 10 years with her." He was kidding, of course. He had a great marriage, loving family, retired early... and the only thing that really bothered him much was the state of his deteriorating golf game.
Eenie had a stroke last fall, spent 5 unresponsive days in the hospital, before the family made the heart wrenching decision to cut off life support, per his wishes. He lived 91 years, and I can honestly say that there will never be another one like him. He broke the mold.