Let's say you are telling me about the 2020 election and the voters involved, and you say that all of the states had their numbers manipulated. You would be truthful to say that of all of the states*

*of the US, which is the scope of your subject.

Other states--the federal states within Argentina, Germany, Russia, whatever--are not the subject of what you've said and so are not referenced within the scope. Yet you've used the word 'all', and you've done so truthfully, soundly. It would be me changing your scope if I demanded every use of 'all' be global, never allowing you to remain in the context you begin a story with.

If I'm talking about a people (the descendants of Adam, as the recounting of Noah begins) and I say "all of the land" (their land), that is a true statement. "The mountains were covered." The statement still remains true. "All of the flesh and plant life of the land died." Still remains true.
Other land--the land where others live--is not in the scope.

The word is not 'Earth' in scripture; it is 'earth'--'land', 'ground'--and specifically the land of the people in the scope, the people discussed by the same text.

The point of the Flood was to chastise His children, to start over, to cut off the branches that were touching the tree of knowledge of good and evil. (Where there is no law, there is no sin accounted. The law given by God to Adam and his descendants was to be fruitful and multiply and to not eat of the tree of knowledge of good and evil--that is, to not have relations with angels. It is for sin--a transgression of God's commandments--that death is resultant and even dealt immediately as punishment. Once more, sin is not accounted where no law has been given. At this point, God has commanded only to be fruitful and multiply and to not eat of the tree of knowledge of good and evil. The Flood story begins with that commandment being once again transgressed--it not being an offhanded interjection that the descendants of Adam are mixing with angels. The explanation for why Noah was chosen given by scripture is that he was not only righteous but perfect in his generations (i.e. not an offspring of this unlawful combining). Importantly, he was priest of the descendants of Adam, being the eighth to be so, the eighth priest, after the order of Melchizedek (oldest living father by the line of eldest sons living, passing from father to son, upon the death of the father).

Transgression of this same commandment is the moment when Sodom and Gomorrah, of whom "their iniquity was not yet full" before, suddenly have their iniquity full. It is when they try to have sexual relations with angels, pressing on the door to rape them, that death is dealt--punishment for the transgression of the same commandment.

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It is a bad argument for someone to claim they lean on "the Traditional Christian understanding." Place yourself on a dart and throw it at the timeline during the OT, and imagine leaning on "the Traditional Israelite understanding" during anytime time during the OT, let alone during the exceptional time of the NT.
Traditionally, we are awful at tradition.
Our faithfulness / skill is no different now.

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I know the following wasn't shared as a "I will die on this hill" view and more offered as a view that's heard, but it is still worth addressing:

Were Noah's sons to have married women of different races, we would run into two major problems to use that as an explanation.
>There are more races than sons
>The families of those sons became nations that scripture names in Genesis 10. These are real nations, and these real nations had a real, historical ethnicity.