I've absolutely been on short/mid-haul domestic flights with FAs who are so junior that it is the first time they have flown a type.
They are sometimes unclear where the demo kit is, and will comment to their flying partner that it is their first time.
Sometimes the newbie ends up working the purser position based on seniority and has to read from their device and still messes it up, just from lack of experience.
I'd say in the past four months I've had this happen twice. Not the entire crew, but crew working up front who were very new.