The Dutch artificial island 'Flevopolder' is ~970 square km. So, I wouldn't say giant when there is an artificial island that has a 373x larger surface area.
But that’s a polder made mostly by building dykes and draining the land rather than raising up the ground level across 970 square km. Flevopolder is about 4m below sea level.
I think the plan here is different and will not be done by building up dykes and draining the area inside.
https://en.wikipedia.org/wiki/Flevopolder
It is still a very nice project nonetheless!