It occurred to me just now that the biggest different at 6-max vs FR is that at 6-max you are forced to play OOP more. I've posted a lot of hands where I made really weak-tight folds preflop for fear of playing OOP postflop. At 6-max, you're forced to play more from the blinds, hence more pots played OOP whether your opponents are positionally aware or not. So, to work on my OOP game, I think I'll play more 6-max.

Also, this might explain why bigger limits have less FR and more 6-max. More players are positionally aware so better players don't get the edge of playing in position whenever they get involved, hence the best intrinsic reason for playing FR, playing in position more often, is nullified.

How's my logic?