The entire change that was enacted into the system was started because the data WDW had showed overuse/abuse of the system, which was effecting wait times and lines.
And of course there is going to be a concern on abuse on attempts to link ticket sales to accommodations. First, the company doesn't want to lose money, either through people refusing to buy tickets if not given what they want, or threatening to return tickets if they don't get what they want. Second, the system shouldn't have any financial incentive behind the determination on what accommodation should be given. It should be money blind. Any link to the accommodation having an effect on profits/sales inherently bias the decision and the system, and would result in overuse...which is what the entire purpose of the change in the system in the first place.
As to not knowing what accommodation a person will get without going through the process...that is inherent in the entire system. Reasonable accommodations are not meant, and the law doesn't require, there being a one size fits all approach. Its supposed to be a reasonable accommodation such that it provides just enough accommodation to the person seeking it, while having minimal impact on business operations and other customers/employees, ect. As a general rule, it is the business that is going to decide what accommodation is necessary. The company is not going to pay of the costs of people to conduct interviews, make determinations, for people who haven't already purchased tickets, either to avoid the increased volume of people who will be tying up the system for "lets just see" calls, or "we want to go someday" type calls, or again people who are going to try and leverage what they think they want, vs what WDW thinks they need for purchasing tickets.