I believe Ten Hag said that to convince himself if he would not be sacked from Manchester United. It's to make sure he's not losing the trust from their fans as well.
Even if they sack him, they would be doing it without sending a notice to him. He can focus on the upcoming games against Porto and Villa. He must deliver in these two important matches. Most probably he stays much longer if his club take three points from their opponents soon.
Even if he is scared of being sacked and he can do nothing caused by its club's decision. No one is bigger than the of club itself.
Maybe he doesn't care whether he will be sacked or not, but it is an unpleasant moment when you are sacked for bad results. Maybe this is how he calms himself down, but it seems to me that he just needed to answer the endless questions from the press, who will ask such questions after every unsuccessful series of matches. But I think that no one will argue with the fact that ten Hag is not coping well with his duties and despite the fact that the season has just started, he can already be sacked and no one will argue with that.