I think part of the problem is, you don't pay attention.
Barbarian, earlier:
You're a little confused. God used "eretz" for the word translated as "earth." "Eretz" means "land." It could mean "my land", "hereabouts", the land of Israel, etc.
It can mean just "earth" (dirt, not "Earth") or it can mean some land somewhere, or "locally" or a specific nation, etc. What it's not used for is "global."
Of course not. That's why it needed to be modified by "kol" to explain that it was the whole earth. That's what makes it global, potentially. And to make sure it was understood, the same word described how much of the heavens the land being addressed was under.
Genesis 8:9 KJV — But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark.
And
Genesis 7:19 KJV — And the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered.
And in case we don't yet get it, Peter explains using a more global word, "kosmos", which is NOT Greek for "land", but for something more encompassing.
2 Peter 2:5 KJV — And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;
But alas, Peter knew many would reject the truth of the global flood:
2 Peter 3:5 KJV — For this they willingly are ignorant of, that by the word of God the heavens were of old, and the earth (land) standing out of the water and in the water:
2 Peter 3:6 KJV — Whereby the world (whole earth, or all the earth, but not just "land") that then was, being overflowed with water, perished:
So, while you are right that eretz doesn't have to mean the whole earth, it certainly
can mean that, especially when modified by whole ("kol").