He's representing the green party. The green party sees itself as being "left". The green party is more popular than the social democratic "die Linke" or any other party that styles itself as "left". The right "realpolitik" wing of the green party has consistently dominated the party line almost since it's inception. So yes, he does indeed represent a big part of what passes as left in german media discourse and in parliament. Truly left movements in Germany have to look outside their leftist bubbles and acknowledge the poor state of class consciousness and organizing in Germany, if they want any hope to improve it.