Does the 120 years mentioned in Genesis 6 refer to the human lifespan?

Below is the context from the NAS. Genesis 6 (New American Standard Bible)New American Standard Bible (NASB) Copyright © 1960, 1962, 1963, 1968, 1971, 1972, 1973, 1975, 1977, 1995 by The Lockman Foundation Genesis 6 The Corruption of Mankind 1Now it came about, when men began to multiply on the face of the land, and daughters were born to them, 2that the sons of God saw that the daughters of men were beautiful; and they took wives for themselves, whomever they chose. 3Then the LORD said, "(A)My Spirit shall not strive with man forever, (B)because he also is flesh; nevertheless his days shall be one hundred and twenty years." The New Living Translation says it this way: Genesis 6 (New Living Translation) New Living Translation (NLT) Holy Bible. New Living Translation copyright © 1996, 2004 by Tyndale Charitable Trust. Used by permission of Tyndale House Publishers. Genesis 6 A World Gone Wrong 1 Then the people began to multiply on the earth, and daughters were born to them. 2 The sons of God saw the beautiful women[a] and took any they wanted as their wives. 3 Then the Lord said, "My Spirit will not put up with[b] humans for such a long time, for they are only mortal flesh. In the future, their normal lifespan will be no more than 120 years." After some research I tend to differ with this translation or the thought that God was limiting the lifespan of man to 120 years. Why? The answer is simple. Unlike Psalm 90 which places the general limit to a man's age between 70 and 80, a thing we can see that has varied widely throughout history, there is no evidence man's lifespan was 120 years (give or take) during this time or after the flood. See the list of ages below for reference looking at the ages of men after Noah. Adam 930Seth 912Enosh 905Kenan 910Mahalalel 895Jared 962Methuselah 969Lamech 777Noah 950Shem 600Arpachshad 438Shelah 433Eber 464Peleg 239Reu 239Serug 230Nahor 148Terah 205Abraham 175 The closest one to 120 years of age is Nahor who lived to only 148! It is clear that the lifespan of man dropped after the flood but we don't see 120 years. What else could have this passage meant? Many have suggested this 120 year period was from the time God revealed that He decided to flood the earth until he actually did it. Noah was 500 when he first mentioned in Genesis 5:32 and in his 600th year when he entered the ark according to Genesis 7:11. While that is only a period of 100 years we do not have a reference of time when God said man's remaining days would be 120 years. It could have easily been a 120 year period for all we know. I would not get dogmatic about this at all. It is very difficult to tell for sure. All we know is man's lifespan did not seem to be shortened to 120 years but gradually was shortened to between 70 and 80 years. I would lean towards this scripture suggesting it was 120 years from the time God made the decree that he was going to destroy life on earth until he did so by the flood, Genesis 6:7.