It's worth a try
I speak as someone who worked depot for a Microage affiliate who serviced name brand PCs (everything but Toshiba) and Apple too. In the early '90s I was a Resource Specialist for a liberal arts college and was responsible for the computer lab repairs of the Mac SE's and Pluses that needed frequent servicing from tehir heavy use.
Working for Microage, if an Apple computer was under Applecare or original warranty, we did not take a lot of time looking for damage caused by accident.
In fact, the only time I remember denying a claim to anybody with a valid warranty was when the user admitted running over his Compaq Prolinea with his car. The main damage were cracks to the case and a loose inverter board. After I told him that constituted abuse and couldn't be covered by warranty, he claimed he was just kidding. When I told him the cracks were consistent with his story he didn't push it. He probably felt like a doofus. (The Compaq still worked fine, they had some tough laptops in those days.)
Anyway, I believe how you are treated depends on how they address the problem. If they pull the screen &/or inverter board and keyboard, they MIGHT see the dried coffee. They MIGHT void the warranty. Or they might simply take the bad parts and return them to Apple, where they likely be disposed of and never even looked at.
If they send the whole unit to Apple, and act only as customer interface, then maybe policies have changed if they have enough cheap help who can take the time to look at the defective part and look specifically for coffee.
Margins are smaller now, but I still think if you refuse to make the mental connection between the spill and the defect, that you can kep your mouth shut with a non-Apple store dealer and likely get service. Even Best Buy would probably be okay. Almost any kind of electrical problem or product defect cancause the problem you describe.
I don't recommend this, but if you wanted to be too clever, you could simply short the thing out with high voltage or damage the zero sector on the hard drive. When they replace the other parts, they won't be looking for coffee under the keyboard.
