Comment by hn_throwaway_99

I'm quite sure they didn't "wait until the end" to do the testing. First, this article is iFixit's speculation. Second, they probably did something similar to what iFixit envisioned: they did test early and knew it didn't pass muster, but thought they could eventually engineer themselves a fix, until they finally just hit a brick wall (aka physics) and found it wasn't an issue they could overcome.