The goal isn't to have a 100% success rate, it's to work most of the time in order to speed up processing.

I believe you are confusing the rationale provided for the goal.

This isn't speeding up an existing process, it's adding a new one. My understanding is that you still need a TSA person to look at your ID when you go through security

I feel like even a mediocre TSA agent is going to be suspicious about the heavily bearded man with a serious bruise on their face. I mean, unless that matches your passport!

What, exactly, are they going to be suspicious about in this hypothetical of yours? Humans are pretty good at matching up facial features naturally, a black eye and beard aren't going to trip up anybody looking at you.

Again, this assumes your passport matches, and humans are trained to spot the unusual. Guy with a massive beard he did’t have on his passport, plus a bruise sufficient to fool he camera is suspicious don’t you think? Once again, this also assumes that being recognized is a problem, which is why you’re evading the scanner.

I don’t see how this works.

Edit: Remember, it can’t be a valid passport that actually looks like you in this case or it defeats the point of the disguise. Remember, this only makes sense if you’re trying to evade detection, and it makes no sense to evade the camera by standing out like a sore thumb to the humans.

You know passports are valid for ten years, right? Facial hair completely not matching the image is very common.

Unlike what border control thinks, you are allowed to look different after 10 years, the picture on the passport is only there for reference and should not be used to identify people reliably.