It’s confirmed that a majority of the water on earth has come from external sources.

What you’re referencing simply indicates that the water was deep within the earth very early on, which is true.

When the earth was very young, and still red hot molten rock, it was being bombarded by asteroids. Jupiter was wreaking havoc on the early asteroid belt sending rock every direction, many of them hit earth and were essentially absorbed into the then molten rock. Over millions of years as the earth cooled that rock sunk into the deeper layers (mantle) of the earth and rose again, depositing the materials, including water molecules. The thin outer layer that we call the crust cooled.

The water molecules only were released via volcanic activity, the first storms on earth raged for, we believe, millions of years. That’s how much water was initially released via volcanoes. Insane to consider.