'Finger placement' IS intonation with fretless instruments. It's a moving target as the fingers move, and is usually off to some degree, plus or minus. It gives depth and character to the sound. That's part of the charm, but it's still off. With a fretted instrument, you're always off the same amount on the notes; without frets, you're off a different amount every time you play that note. The faster you play, the less precise you can be, especially as you move up and down the neck and the note spacing gets larger and smaller. With a double bass, it's a blessing that the notes 'pop' and don't sustain, as that hides some of the intonation errors.
