Based only on the ages in the two William's households I would tend to think neither was "our" guy. As I have no context for a Sarah NOBLETT I won't comment.
I do know that based on anecdotal evidence they SHOULD be in MO by the time of the 1840 census. The various tales about the MURRAY clan imply that they traveled with other family members and that Nancy MURRAY was in MO before 1840 [since she arrived before her husband and he died in 1840]. The BOWMANs believe John BOWMAN and family arrived in 1838 [though the birth places of his children are rather confused as to TN, MO and which came first]. The records I have for Thomas NOBLETT would put him in MO no later than 1842 but no earlier than 1838.
I know Meg's work and she's quite accurate but I have no idea where she might have come up with a William Thomas NOBLETT. I know that I have nothing like that in my files.