The opps spec allows it......so no legal worries...it can be logged... It is 100% ok with the FAA, and they are well aware of it. Functionality they become a required crew member when assigned the trip, and can then Legally log it as per the ops spec's and the FAA. While others might be able to give you more specific info, I can say it is all "above board", nothing sketchy going on.
If I recall right (depending on the program, there are a couple of different variations based on how many hours a person is hired with... prior pages have all the info several times)most get a VFR 135 checkout...then can fly alone in good weather, or trade legs as needed when less than ideal...
Heck...kinda remember getting cut loose in a caravan (different company, different era), at night, alone, and getting into ice and also dodging thunderstorms for the first time in a twin....you learned fast, and made more correct choices that wrong or you didn't survive. Getting to have a few hours with an more experienced captain and getting schooled in real world hard IFR IMO is a great option.... priceless actually.