Perhaps Peter should have been more on the defensive when Tony was ready to blast him but the shock of seeing his mentor and more importantly, his father figure, standing in the room had sent him into a state of shock. He had spent a lot of time wishing for this moment but he knew it would only amount to a wish that would never come true.
As Tony approached him, Peter took a small step back. This had to be another one of Beck's illusions right? Peter was there after the battle with Thanos. He saw Tony's sacrifice and watched him die for it. There's no way that Tony survived. But the man in front of him sounded like Tony and he couldn't help but hope.
Peter approached Tony slowly, his hands resting on Tony's arms, happy to see that they were solid. "You're not an illusion?" He asked before he went for the hug, gripping Tony as tight as he could. "How is this even possible, Mr. Stark?"