No worries, I've got you:)
It's saying IF it ends in extended position, it has to ORIGINATE from the ground... an express up/switch up is the same thing- originates from the ground, switches legs on the way up, so it's level 4 legal in these rules
A low-to-high LIB to STRETCH tick tock, using the "cheat" where the backspot maintains contact with the flyer's leg, is LEGAL because there is not a true release at any point.
A low-to-high stretch to stretch OR a high to high anything would be ILLEGAL because both are release moves and neither originate at the ground.
Hopefully, that makes sense:)