aa777888 - is that the same FAA handbook that called settling with power and VRS the same thing?
Go and try a transition to forward flight on a still wind day from a 15' hover - don't change the power but move the cyclic very slightly forward. You will start to descend as you have tilted the lift vector, then as the speed starts to increase you get inflow roll (transverse flow) which makes the aircraft roll towards the advancing side - correct that with lateral cyclic and you will next feel the vibration of ETL as the rotor passes through the roll-up vortices of the downwash - then the nose pitches up and the aircraft climbs as the rotor experiences cleaner air.
Transvers flow is a flapping to equality in roll that exists throughout the speed range but is most noticeable just after the disc is tilted forwards to initiate a transition. Not associated with vibration.