Universal persistence based on UDP payload - what event to use?

There is no session as such on the application side. The only timeout their protocol specifies relates to a timeslot which all parts of a chunked message should arrive within - and it's 5 seconds. Unfortunately this is not exactly what time-out for an entry in persistence table means.

Though I'm not really concerned about the timeout here. What confuses me is why I am seeing no entries in the persistence table when I am changing iRule event from CLIENT_ACCEPTED to CLIENT_DATA.

As per the screenshot above CLIENT_ACCEPTED events are supposed to be a subset of all CLIENT_DATA event in the context of UDP virtual servers but this does not seem to be the case in my scenario.