In simple words. Kite pull is squared to kite forward flying speed. By allowing kite to fly fast forward it pulls more than suffocating kite by oversheeting via bar getting more AoA but slower flying speed. Your task as a rider is to find optimum forward flying speed and sheeting of bar to get the most out what you want to achieve.
If you look airfoil typical speedpolar (quoted picture is more about wing loading how it affects polar but every airfoil has similar shaped polar, kite or A380 wing) you can see to top point of polar, IMO anything in the left side of it is a waste of energy, so try to fly always at peak L/D speed or right side of speed range. That's how I've reasoned it.
If kite cannot be backstalled it cannot be relaunched. LEI single line pull is backstalling that side of kite to lift it up in the wind. Foils do the same, depending on canopy AR you can single line or dual line backstall to relaunch leading edge down situations. Usually foil & bar travel is tuned so that in light winds fully sheeting in the kite might start backstalling. Just push a bar forward to let kite fly forward as fast as possible and fly via speedy arcs and you get the most power out from foil kite.
You can kite with 15m foil kite when 17+m LEI does not want to fly properly or to turn from edge towards zenith. This video is from pre-hydrofoil-era (2014), me and my 110kg using first time Spleene monster door twintip with 15m Speed4 Lotus kite. As you can see I am not fully sheeting in with bar but trying to get enough power me to glide and kite to fly until apparent wind kicks enough and kite can be parked. Depower is at max power, some people pull depower to eliminate too much sheeting in.