I've heard a lot about "Taliban strongholds", usually from the media. Personally, I've always taken it to describe areas where there are lots of Taliban, where they have a support network in place and some local support and not in terms of fixed strongpoints on a battlefield. As for the staying and fleeing: that's usually the case when they are the one's being attacked and not the one's on the offensive. IOW, I'm not convinced they would suddenly adapt defensive tactics that play right into their enemy's strengths and negate theirs, especially when you consider that fixed defensive positions are a feature of western-style warfare, not the run and gun style of the Afghan tribes.
But yet, that is exactly what they did during operation Medusa.