I think I'm right in saying that the department loads the offer directly onto track - but please correct me if I'm talking rubbish.
I can only speak for the university where I worked, Littleham, and not everyone will do things in the same way, but there the offer would have come from admissions staff, not the department.
There were a number of possible models for making decisions and it was up to staff on each degree programme to decide how to proceed. I don't know how many programmes adopted each of the following, but I do know that there was some pressure exerted to go for 1 in the hope of speeding the whole process up, especially for overseas students.
- Department told admissions what they were looking for and admissions staff did all the rejecting and offering, with just a few non-standard applications going to the department.
- As above, but admissions only rejected the obvious cases, all decisions to offer came from department.
- Admissions staff referred all applications to department with a recommendation on whether applicant was eligible for an offer or not. Department staff then made a judgement on each application and passed them back to Admissions.
Regardless of who was assessing the applications, admissions staff had a lot to do in assessing whether an applicant was a Home/EU student or overseas, checking qualifications and English language competence (not always easy with those who have studied overseas), checking out specific issues to do with visas/disability/criminal records, and so on.
The reason all offers came from admissions staff, not academics or other admin staff, was because once the offer is made, it's legally binding. There had been cases in the distant past of academics offering unconditional places to people who didn't meet the minimum academic standards, or of making offers to people who didn't stand a chance of getting a visa. All very messy.