In the airlines I have worked for a Second Officer, (one bar or ring), is still under training and only fly with training captains, when with a training captain he will get to land the 'plane occasionally.
Bear in mind that this young chap has recently completed initial flying training and has no more than 250 hours to his name, most of which is on very light aircraft.
The idea is to continue the training, accustom them to large jet aircraft, (possibly via a Lear Jet phase in their post CPL course), in order that they can be released to line as a First Officer, (two bars), with a minimum of experience but sufficient to do the job.
Because the market let them do it Cathay Pacific have been employing very well qualified pilots as SOs whilst they learnt the CX way of doing things but in the majority of airlines that employ SOs it is a very recently released from initial training kind of thing, with a natural upgrade to FO as and when progressive checks are passed.