As stated above… the answer to your question is No - USC did not misjudge their projected yield rate… at least not for 2019.
They always aim for a freshman class of circa 3K enrolled. Back in 2014-16, they were relatively good at guessing what their yield rate would be. It was 34-36%. But it jumped unexpectedly up to 39% in 2017 and 42% in 2018. It seems that they expected 41-42% again for 2019, which is why they admitted only 7551 vs as many as 9025 in 2017, for example.
With 3152 commitments this year, the yield rate is 41.7%, nearly identical to the 42% in 2018.
The linked article of course missed the key point that USC is aiming for a freshman class of 3000. 3152 this year is much closer to that mark than 3490 last year or 3528 in 2017. USC is managing the process well… even if those looking in from the outside do not even understand what USC is trying to accomplish.