Park Tools is correct. If you're starting with the L screw loosened and the front derailleur centered over the chain with the rear der on the largest cog, you first have to tighten the L screw to get it to start rubbing the inside cage plate against the chain. Then back off (loosen the L screw) just enough to get it to stop rubbing.
In order to get it close enough to start the adjustments, your cable tension has to be close enough to get you within range. You will fine tune the cable tension after getting the H and L screw limits set correctly, but you'll still need to close to start with.