Ali, your square-bracketed characterization of the 'extra-conceptual content' in Sellars to which McDowell objects is a bit puzzling to me.  Sellars' internalist requirement that the perceiver have a grip on the concept of standard conditions (etc.) is indeed additional conceptual content, but it is not 'extra-conceptual content' in the sense of non-conceptual content; and I think the latter, in the form of Sellars' embrace of non-conceptual sensory representations, is what McDowell (mistakenly) thinks 'distorts our immediate contact with the object in intuition'. 

There is a link between the two, perhaps, in Mind and World, in the reading of Sellars on non-conceptual sensations that McDowell has subsequently, and correctly, abandoned (see his 2009 collection, 'Having the World in View', pp. vii, 19-20, 122).  This was his idea that perhaps Sellars' can bring his theory of non-conceptual sensations into the 'space of reasons' as part of an epistemological theory that posits regularities involved in 'standard conditions' of perception -- but in Mind and World McD rejected this 'sideways on' justification of Sellars' 'sense impressions'.

In his more recent work McD now sees how Sellars thinks he can have both components intrinsic to a perceptual taking -- i.e., conceptual thinking and nonconceptual sensing -- but McD still thinks (mistakenly, I think) that the latter nonconceptual sensory contents still prohibit Sellars from achieving a satisfactory direct realism.  See McD's essay in that volume, 'Sensory Consciousness in Kant and Sellars' in particular, which gives a more accurate reading of Sellars, while still attempting to insist that Sellars' 'two component view' embracing nonconceptual content is unsatisfactory (for example, by in some sense taking colour out of objects and into the perceiver).

Not sure if this helps with what you were worried about...