Originally Posted by: JeffS65[p]I like my other fingers away from the pick. That's also because I learned early on that my picking was sloppy because of it and when I splayed out my fingers away from the pick, I had much better accuracy.[/quote][p]
That's an interesting personal perspective Jeff65. For me, I have superior co-ordination and more control over the pick using a third supporting index finger. But always ready to change if an alternative offers a better way to do something, I'll have to trial investigate and see if your technique offers anything in that regard to me. I'm constantly trying to improve my picking accuracy consistency at speed, and had put it down wholly to achieving that through naturally improving over time with focus and hours logged.
[quote=JeffS65]
I've been playing for decades and always play with a strap even when sitting down. I can, and often have, played with the knee supporting in the curve but I prefer the strap do the supporting the instrument and not me. I feel like I have my hands freed up from supporting the instrument because the strap does that work for you.
That's because you prefer 'those' guitars with a body that could double as a battleship anchor. 
I frequently try to play my LP without, but generally go and get it in the end. No need for a strap with any balanced [u]contemporary[/u] SuperStrat or Tele IME as long as one has some degree of basic coordination & control. 90% of the time I play them without when sitting. I don't find [u]any[/u] difficulty or issue in the transition to standing position with strap with them.
To the OP. Re individual idiosyncrasy. In my experience and observation thus far, rules relating to physicality in playing guitar are adaptive guidelines rather than 'inscribed in stone' law. I think this offers an example of case in point, "we're all built differently, so it's OK" summation in answer to the gist of your post.