According to the information you provided, this phenomenon may be caused by stamen foliation. Stamen foliation is a phenomenon in the process of plant reproduction, that is, stamens differentiate into leaves, thus forming a special plant structure. In the situation you described, this structure may grow in the flowers of osmanthus fragrans, forming a phenomenon that a leaf is embedded in the flowers.
It should be noted that this phenomenon is not a common phenomenon of osmanthus plants, but a relatively rare plant variation. If you have a deeper interest in plant cultivation and plant biology, I suggest you consult a professional botanist or horticulturist for more accurate and detailed guidance.