.swiftinterfaceみると @_Concurrency.MainActor(unsafe) 書いてありますね

@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *) @_typeEraser(AnyView) public protocol View { static func _makeView(view: SwiftUI._GraphValue<Self>, inputs: SwiftUI._ViewInputs) -> SwiftUI._ViewOutputs static func _makeViewList(view: SwiftUI._GraphValue<Self>, inputs: SwiftUI._ViewListInputs) -> SwiftUI._ViewListOutputs @available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *) static func _viewListCount(inputs: SwiftUI._ViewListCountInputs) -> Swift.Int? associatedtype Body : SwiftUI.View @SwiftUI.ViewBuilder @_Concurrency.MainActor(unsafe) var body: Self.Body { get } }

(edited)