Looking at it from an operational point of view, I think (ready for people to tell me how I'm wrong) this was the only thing to do. Before the pandemic happened, training was happening and all was going reasonably well.
Then Covid-19 happened. Suddenly all training, route learning etc has to stop. From my perspective as a trainee driver (with 250+ colleagues in the same boat company wide), it's been if anything frustrating but understandable. We've been waiting 18+ weeks now to go back and continue so that's just one aspect of it.
On top of this there are still a large number of drivers to be trained on the new traction which takes time. This was paused. Route learning has also been paused. On top of this there have been retirements meaning that when services do increase there will be less drivers to operate them. There is nearly 5 months worth of training that has to be caught up now.
Unfortunately for those affected, rather that piecemeal preplanned cancellations that can go drastically wrong affecting the whole network for that day, operationally the best plan overall was to suspend the Rose Hill line temporarily. It's not being closed permanently. It will be back