A lot of modern equipment cannot be adjusted by the end user. They are calibrated in a calibration jig (for want of a better word) where the calibration is done automatically and adjustment values are stored in NV-RAM. I'm not sure if the SDL1020X-E falls into this category, but it is likely.
Also, my guess is the main difference between the X and X-E models is not in the build or calibration, but in stability and precision. In other words, the X-E are identical to the X except they did not pass the noise and stability specs required to resolve the 4th digit, so the digit is disabled and they are sold as X-E models for less money. Again, I could be wrong but I have worked for companies that do exactly this. For instance microprocessors. There is no difference between an Intel i7 rated at 3GHz and one rated at 3.2GHz of the same generation with the exception that the one rated at 3.2GHz worked within spec at that speed, whereas the 3GHz item did not.