NSUserActivity deleteAllSavedUserActivities not working - swift

Question

My case is utterly simple: I use the next function
private func launchActivity(_ id: String, title: String, invocPhrase: String) {
userActivity = NSUserActivity(activityType: "Open_bank")
userActivity?.title = title
userActivity?.userInfo = ["id": id]
if #available(iOS 12.0, *) {
userActivity?.suggestedInvocationPhrase = invocPhrase
userActivity?.isEligibleForPrediction = true
userActivity?.persistentIdentifier = id
} else {
//Can't actually invoke this block
}
}
to create a certain userActivity, and then add it to Siri, so that it can be invoked by by invocPhrase. Here is the function which does this.
func presentAddOpenBankToSiriVC() {
guard let userActivity = self.userActivity else { return }
if #available(iOS 12.0, *) {
let shortcut = INShortcut(userActivity: userActivity)
let viewController = INUIAddVoiceShortcutViewController(shortcut: shortcut)
viewController.modalPresentationStyle = .formSheet
viewController.delegate = self
present(viewController, animated: true, completion: nil)
} else {
//Can't actually invoke this block
}
}
Later I try to delete it (as well as all other user activities)
NSUserActivity.deleteAllSavedUserActivities {}
And it just does not delete any user activity, contrary to what's written in Apple Documentation
https://developer.apple.com/documentation/sirikit/deleting_donated_shortcuts
Actually, at first, I've tried a method
deleteSavedUserActivities(withPersistentIdentifiers:completionHandler:)
with userActivity's persistentIdentifier, but, obviously, also to no avail.
I've no idea why it refuses to budge but would be grateful to any help or hint