Sasuke absorbs the chakraThat scan actually shows that Sasuke knows about his Rinnegan abilities if anything it shows him telling Naruto it's one of his abilities he don't seem surprised at all
Sasuke: This is one of the Rinnegan abilities ....
It shows you that Sasuke did not know he could perform this ability, until he actually performed it. Kishimoto portrays that with Sasuke's monologue about it.
I mean who do you think Sasuke was talking to? You think he was explaining it to Naruto as if he was some copy-cat villian who explains his techniques before he does it? :l