Not all circuits found on the net are good circuits. Many of them have not even resulted in any working product
- the project died half-way with design material that might look ok but are 100% untested.

I have the strong impression that many unqualified amateurs get something together that 'works' (note the quotes) and post it as "see what I have made" or, even worse "see how brilliant I am". Some of them may even be good at web page design and thus make the presentation seem professional.

Erik