It's these media settings that the calibration data presumably alters, not the profile.
Precisely -- it alters the ink settings for specific media in the lookup table to match some pre-established Epson standard.
What it amounts to is an easy way to normalize the minor changes that can occur during paper and ink manufacture, preventing the need for a complete new profile. However it accomplishes this task by requiring the generation of an additional "mini-profile" for each specific media. And I for one question the logic of this process...
Since I only have one Epson x800 printer, and since I only use a few different types of media, and since I already own an excellent spectro, and since it does not take that much longer to print and read my 900+ patch charts, I have decided to simply build a complete new profile ifandorwhen I notice something has changed.