See the discussion at https://www.reddit.com/r/QtFramework/comments/171o2lc/getting_started_with_qt_in_visual_studio/:

People select "LGPL 2.1" and get most Tools greyed out, giving the impression that the Tools may not be used to work on LGPL'ed code.

It is presumably meant that the code of the Tools themselves (usually Commercial + GPL) is not usable under LGPL but this is not interesting information for the vast majority of people coming to this high-level overview side. The typical visitor there wants to work /with/ Tools, not /on/ Tools.