The short answer is it isn't a Sunfish. It's most likely an AMFlite or Windflite. They used the Sunfish hull but a slightly different deck. They were designed to be cheaper to make and sell. It's a perfectly good boat, it just cannot be raced against Sunfish in sanctioned events.
To add to the confusion AMF used the Amflite name for its line of bowling balls .
Funny, I was out sailing when a Windflite (a regular 2-week summer visitor) came out to sail around for a couple of hours. The skipper was about 8 years old."...I'm confused about my boats design compared to what I see online about this vintage Sunfish..."
Is that the original sail? If so do you have a pic with the sail up