There are a few left hand positions in flamenco that I had never encountered in classical guitar. For instance, you at times may need to play the 4th fret of the 6th string with your index finger while simultaneous playing the 3rd fret of the 2nd and 3rd string with your pinky and ring finger. The end result is your index being positioned higher up on the neck than your pinky and ring finger, which is uncomfortable to say the least (this most often occurs when playing the alzapua technique).
That being said, it is true that most of the techniques that are specific to flamenco are right hand techniques. Some of them also exist in classical guitar but are not used in the same way or to the same extent. For instance, in flamenco guitar, the thumb does almost exclusively rest strokes and hardly any free strokes.
To finish on the left hand in flamenco, there are certain hand positions that are extremely common. These are not techniques per se, they are simply different chord voicings that are widely used in flamenco but that are uncommon in other forms of guitar and that you must learn to play actual flamenco pieces. If you only learn the right hand techniques, then you will only be able to play non-flamenco pieces and make them "sound flamenco" (for instance, playing "Recuerdos de la Alhambra" with a 4-note flamenco tremolo). If, however, you want to play a piece by Paco de Lucia, then knowing the commong left hand positions in flamenco is important.