I have literally zero clue as to how that ETH/WETH smart contract work but... Why the heck did the guy not first did a test with 1 000 USD worth of coins inste

I have literally zero clue as to how that ETH/WETH smart contract work but... Why the heck did the guy not first did a test with 1 000 USD worth of coins instead of 500 000 USD? Once he sees everything is cool with 1 000 USD, he sends the rest. Sounds like 101 to me.