At 1% you're literally on death's door. He's either exaggerating or just making this story up from whole cloth. My guess is it's one of those cases of "the older I get the better I was".
Agreed, 1% body fat is extremely dangerous and your body does not have enough fat for it to go about its normal processes. It is certainly not sustainable for any period of time. Professional bodybuilders have trouble getting down to ~3% body-fat for their competitions and they only have to hold that level for a day or 2.
