I'm going with victim blaming. To me, this hinges on why the fact (with a mitigating appearance) is offered. If it's to show guilt of a lesser evil, that's not victim blaming; if it's to show he's not solely and absolutely 100% in the wrong, then it is.
The actual declaration of the fact does not alone demonstrate victim blaming (I grasp that), but couple that fact with the why is how to get our answer.
Illustration:
If one says her skirt was provocative, that information alone is insufficient to determine that one is attempting to blame the victim. It doesn't look good (that's for sure), and if one goes on to say this never would have happened if she wasn't dressed so provocatively, it's going to take a herd of horses to convince me it's not victim blaming. However, the truth is still the truth, and the truth still hinges on just what I say it does.
A willingness of a child to acquiesce to an adults sexual wants in absolutely no way implies legal consent. If the perpetrator of a sexual assault brings up the victims frame of mind as if it was a pleasurable welcoming experience (by saying the child liked or enjoyed it, or the child wanted it or asked for it), then we still need to know why the perp is saying those things.
If it's because he wants to downplay his crime (like a murderer saying the victim didn't suffer or like a rapist saying the victim was willing and not subject to bloody violence), then that's just a way of saying things could have been worst and so a way of him to say that he's not as bad a person as another might have been.
If it's to mitigate his responsibility by showing that he's not solely the guilty party, then yeah, that's victim blaming all day long.
A way to help narrow down motive for such facts being offered is to consider context in which truths surface. Voluntarily exclaiming in defense is vastly different than answering in direct questioning.
Example 1) did she come into your room? YES
(Hard to conclude victim blaming)
Example 2) this is ALL your fault! SHE CAME INTO MY ROOM!
(Easy to conclude victim blaming)
Example 3) Why did you prey on her? SHE CAME INTO MY ROOM!
(Need more information)
So, victim blaming or not depends on WHY what's being said. To shift blame, yep, but if it's to downplay the crime, nope.