Noah has apparently done everything God has asked of him thus far. God has said he is now righteous. I find it interesting upon further inspection that God orders him into the ark as a final "command" and then states that he is righteous.
I wouldn't agree with this timeline. Please consider:
Gen 6:7-9 The LORD said, "I will blot out man whom I have created from the face of the land, from man to animals to creeping things and to birds of the sky; for I am sorry that I have made them." But Noah found favor in the eyes of the LORD. These are the records of the generations of Noah. Noah was a righteous man, blameless in his time; Noah walked with God.
Noah was "right with God" (righteous) BEFORE the ark was even discussed. It even says "Noah walked with God" much like Enoch.
I liken Noah to Abraham. Abraham simply believed God and it was credited to him as righteousness (Rom 4:3) but he was also justified by his works but much later (James 2:21).