Most big box store employees I ever talked to have no idea how to navigate the menus past volume and input selection so there may not even have been any intentional monkey business.
So who knows. If it's a concern, go back and get them to show you that all the processing is turned off and try again. Might be fun to watch them try and wiggle through it if nothing else.
In the end, as I just wrote in another post, doesn't matter what your technical view is on weather or not all similar receivers are transparent or not, get what makes you feel good about your purchase. Happiness is the end result you are shooting for, is it not?
As a side note, I can attest to having a friend who quit a job at a big box store who admits he was 'coached' into manipulating the brightness controls on the TVs depending on which model they were pushing that week.
