Since over 65% or the windows are installed improperly, it is not surprising that some people try to exercise control and limit liability. Some G.C. will not have their own carpenters install windows and exterior doors, but chose to have them installed by a certified window installer. This has been cause by the number of past claims/loses that have been decided by the courts or insurance companies. Moisture and mold problems get very expensive when they finally get discovered.
Some manufacturers do not want to get involved in disputes over just to sell a window or two and want to control the use including installation.
Your case seems to be a little bit of a sham, but you can always hunt elsewhere for some similar.
Last edited by mudmixer; 09-15-2009 at 08:48 AM.