SwiftUI 4 ShareLink SharePreview unexpected behavior

When integrating the new ShareLink into my project, I noticed two unexpected things. First, when I pass a SharePreview to my sharelink with just a title and no image as a pararameter, my AppIcon suddenly loads in the preview. Is that normal?

Just with that code:

                    ShareLink(item: appStoreUrl, message: Text(["", ""].randomElement()!), preview: SharePreview("ProTimer")) {
                        Label {
                            Text("ProTimer weiterempfehlen")
                                .tint(.primary)
                        } icon: {
                            Image(systemName: "square.and.arrow.up")
                        }
                    }

My second question is, why can't I pass a subtitle in the SharePreview, only the title in bold?