And I am sure, that volume will be nothing compared to those big whales which buy/sell 1000s of Bitcoins every day on CEX or DEX. Nothing will happen due to his selling.
The rest depends upon how users take it.
I agree with you, nothing will happen to bitcoin and to the market when Satoshi sells his bitcoins. He holds a lot of bitcoin but that's compared to us, but compared to the total supply of bitcoin as well as the market, that's nothing.
It has always been said that bitcoin is independent and will not be influenced by any individual or organization. But the funny thing is that people are afraid that Satoshi owns 1 million bitcoins and will sell it. That shows that people don't have as much faith in bitcoin as people say every day. For me, let him sell all those bitcoins, I believe the market will absorb all those bitcoins easily without any problem.