HG your description is close to what I have. Obviously, until Eton give a full details of admission process, one's experience and hearsay could be a clue to a complete picture.
What Eton, and other public schools with competitive entrance system, is trying to do, is to balance between a finance and academic quality of pupils. All applicants are graded. Weighting factors among school report, interview, and computerised test, are not known, though.
The school, then, balances between the grades and bursary requirements, within the pupils with conditional offers. Bursary applications are reviewed a couple of times until the year of entry. Some registrations could be turned down each stage. If many good applicants need financial support in certain year of entry, Eton tends to look for academically equivalent but more affordable applicants from waiting list, and vice versa.
Even if Eton has fairly deep pocket, it has a limit for each entry year while keeping the quality of inlets. For Eton, it is quite clever system, but for applicants in waiting list, it depends on the situation. Even if one is offered the place from waiting list, financial support, if needed, can be limited. In this turbulent economic situation, I presume needs for financial support may increase.
I believe many boys in waiting list are capable of getting scholarships or any kind of financial support. If it is the case, value between such achievement and name value of Eton (or its ethos) would be judged by individuals.