I do understand and appreciate what you're trying to say.
But for it to work it still requires that we deny the plain, literal meaning of Scripture.
Your theory requires that when we read this in Gen. 2.14....
14 The name of the third river is the Tigris; it runs along the east side of Ashur. And the fourth river is the Euphrates.
.... that instead of taking Scripture at face value that we...
well, we can't even actually apply your theory to this verse, because this is not a Post-Flood reference to the Tigris River like Daniel 10.4...
4 On the twenty-fourth day of the first month, as I was standing on the bank of the great river, the Tigris,
Here, you could reject the plain, literal meaning of Scripture with your theory and say that the "Tigris" Daniel is standing beside is not the same as the Pre-Flood Tigris River mentioned in Genesis 2.14.
But that doesn't work with Genesis 2.14, because Genesis 2.14 is speaking about the Pre-Flood Tigris River and indicating that is still identifiable in relation to a Post-Flood ancient city.
But even the Daniel 10.4 verse requires denying the plain, literal meaning of Scripture.
It is similar for the Euphrates River. There are 30 references to the Euphrates River in the Bible. The Bible says the Euphrates River was one of the four rivers associated with the garden of Eden (Gen 2.14). The Bible identifies the Euphrates River as marking the eastern border of the Promised Land in God's covenant with Abraham (Gen 15.18). Even in Revelation, the Bible identifies the Euphrates River as the river that the six bowl judgment will be poured out on, drying up the river (Rev 16.12).
Let me ask you a serious question: if you were born on a deserted island with nothing to read but the Bible and knew nothing about science or geology or any other subject and all you had to go by was the Bible. Based on the Bible alone, would you think the Bible was talking about completely different rivers with the same name? (And if so, what *in the Bible* would lead you to believe that?). Do you believe Moses wrote the first five books of the Bible like tradition holds? If so, why then does Moses make seven references to the Euphrates River in the first five books without clarifying that he is speaking of two different rivers with the same name if that's what he really intended for us to understand?
Genesis 2:14 NAS
14 The name of the third river is Tigris; it flows east of Assyria. And the fourth river is the Euphrates.
Genesis 15:18 NAS
18 On that day the LORD made a covenant with Abram, saying, "To your descendants I have given this land, From the river of Egypt as far as the great river, the river Euphrates:
Genesis 31:21 NAS
21 So he fled with all that he had; and he arose and crossed the Euphrates River, and set his face toward the hill country of Gilead.
Genesis 36:37 NAS
37 Then Samlah died, and Shaul of Rehoboth on the Euphrates River became king in his place.
Exodus 23:31 NAS
31 "I will fix your boundary from the Red Sea to the sea of the Philistines, and from the wilderness to the River Euphrates; for I will deliver the inhabitants of the land into your hand, and you will drive them out before you.
Deuteronomy 1:7 NAS
7 'Turn and set your journey, and go to the hill country of the Amorites, and to all their neighbors in the Arabah, in the hill country and in the lowland and in the Negev and by the seacoast , the land of the Canaanites, and Lebanon, as far as the great river, the river Euphrates.
Deuteronomy 11:24 NAS
24 "Every place on which the sole of your foot treads shall be yours; your border will be from the wilderness to Lebanon, and from the river, the river Euphrates, as far as the western sea.
Joshua 1:4 NAS
4 "From the wilderness and this Lebanon, even as far as the great river, the river Euphrates, all the land of the Hittites, and as far as the Great Sea toward the setting of the sun will be your territory.
1 Kings 14:15 NAS
15 "For the LORD will strike Israel, as a reed is shaken in the water; and He will uproot Israel from this good land which He gave to their fathers, and will scatter them beyond the Euphrates River, because they have made their Asherim, provoking the LORD to anger
Revelation 16:12 - The sixth angel poured out his bowl on the great river
Euphrates, and its water was dried up, to prepare the way for the kings from the east.
Revelation 9:14 - Saying to the sixth angel who had the trumpet, “Release the four angels who are bound at the great river
Euphrates.”