Transverse flow doesn't produce vibration, the onset of ETL does. They often occur at the same time but transverse flow is most noticeable in the early stages of the transition from the hover. A good demo can show the seperate effects of the two but you will only get vibration with the ETL part.
There is no roll-up vortex to fly through in OGE so the vibration from said vortex doesn't occur.
The explanation of the transverse flow vibration in RVDT's second link doesn't hold water - though the rest of the text seems sound.
ETL2GO - you are right - the R22 experiences vibration through the onset and loss of ETL just like any other helicopter.
Transverse flow is a factor across the whole flight envelope not just the transition which is why the R22 has the litlle pull-up knob to offset cyclic lateral loads in forward flight.