Props to you for at least putting "to an extent" in your jury conclusion, most people don't bother with that. However, I'm not sure that the way that you summed it up tells the whole story.
Sandusky was convicted on four of the five counts with respect to Victim 2. They were:
Count 8: Indecent assault
Verdict: Guilty.
Count 9: Unlawful contact with minors
Verdict: Guilty.
Count 10: Corruption of minors
Verdict: Guilty.
Count 11: Endangering welfare of children
Verdict: Guilty.
He was acquitted on one:
Count 7: Involuntary deviate sexual intercourse
Verdict: Not guilty.
Here's the statutory definition of indecent assault in PA:
A person is guilty of indecent assault if the person has indecent contact with the complainant, causes the complainant to have indecent contact with the person or intentionally causes the complainant to come into contact with seminal fluid, urine or feces for the purpose of arousing sexual desire in the person or the complainant and:
- the person does so without the complainant's consent;
- the person does so by forcible compulsion;
- the person does so by threat of forcible compulsion that would prevent resistance by a person of reasonable resolution;
- the complainant is unconscious or the person knows that the complainant is unaware that the indecent contact is occurring;
- the person has substantially impaired the complainant's power to appraise or control his or her conduct by administering or employing, without the knowledge of the complainant, drugs, intoxicants or other means for the purpose of preventing resistance;
- the complainant suffers from a mental disability which renders the complainant incapable of consent;
- the complainant is less than 13 years of age; or
- the complainant is less than 16 years of age and the person is four or more years older than the complainant and the complainant and the person are not married to each other.
That sounds like the jury believed something pretty nasty was going on in the shower. And since, Mike McQueary was the only witness to testify as to what happened there, the jury clearly believed him.
What the jury acquitted Sandusky on was the involuntary deviate sexual intercourse. Deviate sexual intercourse encompasses oral and anal sex (among other things). To be convicted of that charge actual penetration (either orally or anally) must have taken place. So while it's fair to say that the jury refused to convict Sandusky of an actual anal sex act, likely due to the fact that McQueary testified that he did not see anal penetration, I believe it's a stretch to say that he wasn't convicted of a sexual assault. He was convicted of indecent assault for the purpose of arousing sexual desire. That sounds like a sexual assault to me.