A.
This rumor about insulating glass circulates regularly. It is inaccurate for several common-sense reasons. Insulating glass is manufactured as a sealed unit using a chemical desiccant incorporated into the spacer. As time passes, the seal can deteriorate, allowing moisture to seep in. Eventually the desiccant is saturated and the excess moisture appears as the fog in your windows.
Why not open up the unit and remove the moisture? Several factors preclude such an approach. First, moisture trapped on glass actually etches the surface. Thus, even if the glass were scrubbed clean, a slight haze would remain. In addition, there is no reliable way to salvage or replace the desiccant outside of a professional shop, so any "refurbished" insulating glass would be likely to fog up again on some subsequent cold day.
Finally, glass being what it is, it is all too easy to break a pane while trying to service a unit and, at that point, one has wasted any time invested in the project.
Alternatively, Western Window Service installs replacement insulating glass in nearly all kinds of windows with a written ten (10) year warranty against fogging on clear units. .