Eric
I have not noted this on my singles before, I'll watch for it.
I have 2 that I call poodle tails (pics below).

{{gwi:479302}} {{gwi:508785}}
The red one is named "El Capitillo Red",the peach one is from walmart and did not come with a name. both have petals on the pistils (sp). I just looked at a double and it appears that petals on the pistils are a norm for them.
perhaps your plant will produce doubles for you.
Maybe the experts will chime in here in a bit.
pa

Eric: I have also noted this phenomena on some of my Hibiscus. I was also wondering why they did this but I have no answer for you. Somewhat strange but apparently quite normal?? Ross.

Just one of the fun, odd things our hibiscus do sometimes!!