Doubt if he is boosting his figures by doing an easy op rather than a difficult one.
I suspect the admissions clerk (if that is what she is) doesn't know why the operation has been marked as to be done by the consultant only, so don't blame her.
Probably the Consultant cannot trust his junior to do the operation him/ herself (sometimes they get very junior juniors allocated to them, so can't leave anything to them. Also, it is required now that surgeons do NOT leave registrars to operate unsupervised, they are supposed to in training, and until fully trained must be supervised. Or maybe he doesn't have a registrar at all at present, it happens. Or maybe the registrar and consultant are taking leave at the same time.
BTW, unless waiting lists are amazing in your area, or your ds is an urgent case, I wouldn't expect a date to have been set yet- typical waits are around 6 months in our area.
As for the consultant's holiday, if he is taking a long summer holiday, it means that he has less leave throughout the rest of the year; they only get a maximum of 6 weeks a year, and he's entitled to take it when it is convenient for him and his family, as long as there is someone else around to deal with emergencies.
It is unusual for another consultant to operate on a Consultant's patients without a special arrangement between them- they have their own lists, so I wouldn't expect another senior surgeon to do yor ds's op just because one is on holiday.
I suggest you speak to the consultant's secretary and explain your concerns, there may be a simple explanation.