I looked into it, and this is the answers I found in another chin group when people asked about sunflower petals
"Avoid sunflowers altogether. They are very oily. It's not the type of oil that's best for chins."
"The current thinking though, is that since this is a heavy oil, with absolutely excessive saturated and unsaturated oils both, and huge amounts of vitamin E and K,
It's going to contribute to a sludgy fatty liver. Chinchillas are prone to fatty liver disease anyway, it's very common, sadly.
Large amounts of vitamin E are also a problem."
If their is enough oil and vitamins in the petals to cause an issue or not I don't know for a fact, but with so many other safe options I don't think it's worth the risk.

I have only recently been seeing people asking about them and them being in herbal rodent treat mixes so I think more long term study of them needs to be done to know for sure.