When disconnecting pigtail from an empty cylinder there should NOT be any propane leaking otherwise the full tank would equalize with the empty one if empty cylinder service valve was left open.
Lever swaps porting for Indicator NOT which cylinder is being used....1st one valved in denotes which cylinder is being used
LP Pigtails no not have backflow preventors (check valve to stop LP Flow back out of pigtail)
LP Regs typically have those in fittings where pigtails connect.....
If pigtail is Directly connected to REG then no backflow check valves

Pigtails have 'flow limiting' check valves to minimize flow from cylinder to RV LP System should a LEAK happen downstream of REG
