Bear in mind that DVI is a digital interface. There's a protocol involved, and I bet that part of that involves specifing scaling(I'm not going to register with the DDWG to get the spec, can someone confirm this?). I did look up your panel, though, and found this:
The second bulleted item states, "Displays a native resolution of 1280x1024 for incredible detail and clarity[haha] lower resolutions are scaled to full screen using a third-generation processor with variable sharpness control"
I bet that NVIDIA's driver on Linux is opting for the panel scaling by default. Here's a lame review of my screen:
I didn't know that scaling was an option that I could turn on and off! When I get home today, I'll give that a try and let you know how I fare.