[olnluis]

You'd use a lined fretless bass this way, so it might have been a lined fretless guitar on that drawing!

Also, when you're pressing a fret, the pitch isn't coming from where you have your finger, but from the following fret which is making contact with the string. You can actually press the actual fret instead of the area between the fret and the one before it, and it should sound the same.

Now if the person that drew this knew that, I don't know.