It seems to me that the OP should do two things...
First, figure out why said person/people are seeming to get retroactive relief and seeming to have to do LESS work than the average student and what exactly was the specific nature of the accommodations that were proposed that makes it seem unreasonable.
Second, if this has occurred in the past, that said person/people don't do any work and then wait until later on to either go to the disability office and seek accommodations or wait until late in the process and spring the I have a disability and I need these things done to 'help' me.
OP doesn't say if they are a student or teacher...so that means two different things.
A student is kind of limited in what they can do...other than complain to the powers that be about the perceived unfairness and perceived nature of gaming to system that is thought to be going on.
As a teacher, they could talk to the disabilities office about what they have recommended and how it's somewhat unreasonable -- and can we hash something out that's reasonably fair. Also, something that means that the student doesn't get LESS work, maybe in leu of doing X, they need to do Y, which is slightly more /equivalent amounts of work.
Additionally, they could explore the patternality of the 'requests' --that late in the system, requests are being asked for...and possibly wanting retroactive relief.
As a teacher, they could also pretty much state that accommodation requests should be tendered early on in the process and that would allow the teacher to fold them into their teaching/testing style and processes...e.g. do I do X for a single person or do I for everybody.
Also state that late accommodation requests would NOT be retroactive and that would be evaluated on a case by case basis depending on WHEN the request was received (and subject to the teacher talking to the disability office)...Ok, so maybe you'd be somewhat receptive if the request came after the start, but not too far in (when maybe a student figures out they'll need help with how you do things, that they didn't anticipate) but, very late, you'll be more suspicious of.