wait for existence in UI testing

BaseTestCase+waitforexistence.swift

import XCTest

class BaseTestCase: XCTestCase {

    let app = XCUIApplication()
    
    // ...

    func waitforExistence(element: XCUIElement, file: String = #file, line: UInt = #line) {
        let exists = NSPredicate(format: "exists == true")

        expectation(for: exists, evaluatedWith: element, handler: nil)
        waitForExpectations(timeout: 30) {(error) -> Void in
            if (error != nil) {
                let message = "Failed to find \(element) after 30 seconds."
                self.recordFailure(withDescription: message,
                                   inFile: file, atLine: Int(line), expected: true)
            }
        }
    }
}

how is this better than waitForExistence? is it faster?