Can I keep my rounded hairline after a forehead lowering?

I naturally have a rounded hairline, and I'm looking at getting a forehead reduction soon. I notice that in a lot of the after photos, their rounded hairline turns to a straight hairline. I feel that is a bit masculine looking, and I want to keep my exact same hairline, just lower. I don't want it to be straight. Can you explain to me why it turns straight afterward? And if there's a way to avoid that to maintain my same shape? Thanks :)