Can anyone explain why a test transaction is needed?

A whale/institution purchased 1,162 BTC and suspected that Binance was used for test transactions

According to Lookonchain monitoring, a whale/institution purchased 1,162 BTC worth $69.56 million, and another new wallet withdrew 1,162 BTC from Binance 2 hours ago. They were all new wallets created 6 days ago and used Binance for test transactions.

Address: bc1qdtmav38lca8yu3rrcknnqx5242cckgxqws7m72

$BTC