Also, I like how you address the double bass ergonomics. That crossed my mind last night. It's a totally different thing than electric, but it seems people want to equate the two for hand position. I'm not quite sold on that yet. Thanks, Fergie!
In that I play both Double bass and electric, they are physically very different instruments. However, the biggest difference regarding the left hand is in the rotation of the shoulder, elbow, and wrist. All the same basics apply; finger/hand shape, thumb position/shape on the back of the neck, shifting/pivoting, using big muscles (shoulder/back) rather than tiny muscles (hand, thumb), etc. Those things become amplified on the DB many times over the EB, but the same principles of ergonomics apply. You can get by with poor LH technique on the electric bass, but that same poor technique on upright will, at the very least, prevent you from having any facility on the instrument, and at the worst, will cause physical damage to your body. Applying good DB technique to electric will only give you additional facility on EB.
That is not to say that we all have to play exactly the same way; it is only to say that the principles of good ergonomics must be applied to each individual player to find what works best for them. Some things are universally true, though; bent wrists, collapsed/mashed hands/fingers, etc, are physically very limiting, even if they don't physically hurt.