Here are some links, some pretty technical, that explain the corrosion mechanism of glass.
One of the links discusses glass corrosion tests using sulfuric acid commenting that sulfuric acid mimics pretty well the corrosion that glass undergoes when exposed to atmosphere ("...the treatment with sulfuric acid mimics well the atmospheric weathering..." )
For those that remain confused by the technical explanations, just accept that there are scholarly studies that investigate corrosion of glass due to atmospheric exposure as well as exposure to certain chemicals. The PPG article (intermittently highlighted in red) is perhaps the most comprehensible to those of us that lack the technical expertise.
It is probably best to accept Leica's offer to do the wet cleaning at no cost until they work out a permanent fix to the sensor cover glass corrosion.
Sensor cover glass corrosion? Believe it.
Corrosion - Wikipedia, the free encyclopedia (scroll down to 10.2 Corrosion of Glass)