I think your analysis is spot on, Steve. The pictures that Jerry have provided us only really shows two cards that are probably mistakes...the first two. We have to remember that SGC only recently started grading with half grades (for the most part) and I believe if the card was closer to a three than a two, they would grade it that way.
There's no doubt every company makes mistakes on grading, but IMO SGC makes slightly fewer, making them my choice for the most part. I used to believe and heard that SGC only allowed cards with paper loss to receive nothing higher than a 1.5, but I have seen 2's consistently with paper loss...not sure how I feel about this, but I don't completely disagree I guess
Also, I know there are collectors that don't love SGC when they first started grading and believe their grading standards weren't as good...maybe some of their more mistake prone graded cards were during that era???