As a typographer, sometimes i just release some weights of the font but not the entire family. So no, sometimes they're really a professional work.
No, they are fonts that the font designer decided to contribute to society. Quality varies from poor to outstanding.
At some level, all fonts are incomplete. The potential of libre fonts is unlimited, while the potential of non-libre fonts is limited by the proprietor.
Lies, misinformation and too little googling.
They are as good, made with love and care.