Question about telltales - how close to the wind?

Thread starter #1
as someone that like understand how things works I would like to understand how to interpret telltales. I read this article:
Focus on ANGLE - The Key to Upwind Performance - International Sailing Academy
And it is very nice, but I actually would like to ask few questions, to ones that know more then me. So what is puzzling me is this:
* leeward telltale almost never flicks - does it means that separation buble is before it?
* I would say, that flicking windward telltale is indicating laminar flow turbulence - why it is worth to sail like this?