If Andre Onana comes that is a different story, but Manchester United is not all set if they start into the new season with only young goalkeepers. I guess that is why they stl keep the option with De Gea as some kind of joker. But De Gea won't play that game for very long and I assume he will make Manchester United bleed hard financially if they have to decide and offer him another new contract. He won't sign a contract below his expectations.
Over reliance on Degea almost gave Teng Erik a hypertension when he thought of making it among the top 4 was squashing out right in front of his eyes, it took lots of combine effort and extra calculations before they got to that spot again and he doesn't want to repeat this mistakes again, he is taking his chances to source for another good goalkeeper and as Onana is available in the market, they are putting extra effort to bring him to Manchester United but De Gea unofficial announcement and what to expect in the future is not available, the club and him are not saying anything and that is why people think they Manchester United may still need De Gea.
Well so far the most recent news is that Manchester United raised their offer for Onana, but a deal has not been signed yet. That means De Gea is still in the game and it is even better for him if a new deal takes time as that also poses the risk for Manchester United that De Gea goes elsewhere and Inter then knows that they could raise the price for Onana even further. I wouldn't count on De Gea waiting until Manchester United made their final decision. He will also see what the market is doing and try to sign a good contract with a new team if that is what suits him best. Ten Haag has to express his distrust or otherwise he wouldn't want a different goalkeeper and if it doesn't work he suddenly has to trust De Gea again.