I don't normally like to wade in into a disagreement between posters, but I think you're being harsh.
I have to admit, that I also wouldn't really say that he "had it covered", and I think that had it been an inch or two more to the left, that would have been in off the post.
More to the point, I certainly don't think it that it such a clear case of "having it covered" that you can "choose to be far more condescending if wish to"
Well, you can choose to be as condescending as you want, I suppose - but the fact of the matter is, that there is no definition of what "having it covered" actually means, so it is a subjective take on the situation.
For me, I 100% would NOT describe a situation where a goalkeeper desperately lunges full stretch to reach for a ball that passes him at speed, striking the post, rebounding into play, being lucky that the ball doesn't bounce back off him and into the net.. as "having it covered".
Would he have saved it if the ball was a couple of inches further to the left? Maybe, maybe not.
But you're talking to someone like they're stupid for "not getting it", and I definitely don't agree with that.
Was he wrong when he said Heaton was nowhere near it? Yes. But he has already acknowledged that.