Too soon, he was training and playing the whole time since last season. He had one week of rest before Euros and a week now. He won't last long, this season will be full of injuries for him, idiots!
Before insulting, use your head for a few seconds at least.
First of all, he played 43 games last season, far from Pedri's 70+ insane season. And in many of these games not more than 20-30 minutes. In total 2000 minutes, that's 22 full games. A low number in total for today's time and not in risk of any injury, even if you add his olympics games. In comparison, Lamine played 3000 minutes with 16.
Secondly, he's already 21 years old, doesn't have an unstable teenager body that still grows.
Thirdly and most important, it's his own decision. The club doesn't force anything. He doesn't want to miss the start with the new coach. His fear is understandable, because we have many options in his position and after that summer, he has the ambition to play more.
All 3 things combined it's perfectly acceptable to let him start the season. He won't reach too many games this season anyways given his competition, especially when Gavi starts to play.