I recently confirmed that Gemini does indeed offer free withdraws and does not charge transaction / network fees. I'm surprised by this because transaction fees on the Ethereum network can cost over $10 for small transactions (e.g., under $50), which is cost prohibitive. It seems many exchanges, including Coinbase, also offer this free service.
Gemini has some internal software to make it cost efficient for them by rolling withdrawals into one transaction. So when you refer to your transaction hash on Blockchain.com, you'll see a few other transactions alongside your's.