I didn't notice anything wrong with the hand positioning in the photos. The last one I wouldn't be able to play anything and I wouldn't think anyone could play with a straight wrist unless you're fretting the bass note with the thumb.
Pressure you are exerting is most likely something to look at. Thumb behind the fretboard or where ever you need to place it the fact is to much exertion will lead to all kinds of wrist problems and even tendonitis. Looks like you got some good advice from SL though.
All the best,
Joe Pinnavaia
http://www.joepinnavaia.com