I think that's really mean. The language in health care is really confusing. 'Junior', 'Trainee', 'Student' all sound like they have very little experience. Would you trust your finances to a 'trainee advisor'? The fact that these surgeons are actually very experienced isn't obvious.
@RunningThroughMyHead I used to work in a specialist theatres recovery, so spent a lot of time in theatre, and I also did my return to practice placement in general theatres.
Firstly, know that the theatres team is a lot bigger than the surgical team. You'll have an anaesthetist and an OPD who are caring for your DS's physical state during the operation. Before surgery starts, the whole team will have a 'Time Out' where they agree who the patient is, what operation is planned, any complications to be aware of, and who everyone in the team is.
You'll have a scrub nurse who is handing the surgeon everything they need and supporting them as they operate. A circulating nurse makes sure that if anything extra is needed, or equipment is needed, it's available.
Surgical trainees start by observing surgery. Then they may be invited to do a layer of stitching, or a defined part of a surgery. They never just dive in and operate.
The fact that you've been told this surgery is tricky and delicate, means that the surgeon who operates will be experienced. They may be a 'trainee', but all that means is that they have a formal contract with the hospital to give them the training they need to qualify in their speciality. Specialist training contracts are competitive and they will have done huge amounts of study and gained lots of experience to even qualify as a candidate.
Ask the questions - the Consultant's secretary would be a good place to start. They'll be able to give you the information and reassurance you need.