You're right, in that I cannot find anyone claiming the significantly lower figure for CS admissions in particular. Even at 10%, it is among the most competitive programs in the country. Both Williams and Amherst, the top two liberal arts colleges in the US, have over 15% admissions, while Yale and Harvard come in usually between 8% and 10%.
On a side note, I have some doubt that the admissions process is truly blind to your stated major of interest. These schools do have a desire to maintain balance between their programs.
They're not blind, but you can also put down anything you want, including "undecided". I was certain I wanted to be a physics major when I applied to college. Things change.
On a side note, I have some doubt that the admissions process is truly blind to your stated major of interest. These schools do have a desire to maintain balance between their programs.