I have grown many Sativas, and they had many single blade leaves in the budz but they weren't reveg leaves. It's obvious.
This was a plant I pulled a few months ago. Plenty of single blade leaves, but not with elongated petioles and complete lack of serration. The shiny leaves in OPs picture are also a tell tale sign of reveg, whether it's due to nutrient shock (normally nitrogen toxicity), lighting inconsistencies or stress.
This is Sativa stack single blades, and I've grown around 7 of these over the last two years, so yes, I do understand the structure of a healthy Sativa plant.