Brennan's same day affidavit description of a slender white man of about average height who appeared about 30 years old doesn't rule out Oswald
and thousands of other people.
and out of the people we know who were in the building at the time, the sample size wasn't exactly huge
How do "we" know who was in the building at the time?
and let's not forget that Brennan did identify one or more of the black men in the windows directly below as they walked out of the building.
That's what Brennan claimed. It's debatable though. Did Sorrels ever corroborate it? I believe Norman was the only one who mentioned something like this and it's not clear from Norman's account if he recognized them as individuals or because it was 3 black men coming out of the TSBD together.
And it's not really kosher to use a person's own claim to make an argument for that same person's veracity. It's circular.
But regardless, it's not even a good comparison, because Norman/Jarman/Williams were hanging out of the windows and not crouched down behind boxes aiming a rifle for the head shot.