Why tell blatant lies? The BSW is a moderate left leaning party with social capitalist and very conservative ideas about immigration. They‘re also Russia friendly, who are imperialist invasors. Nothing about them is left.
It‘s the opposite, all the traditional middle class types left „Die Linke“, who are now the clear far left candidate. They are the only candidate that propose a socialist economic reform, open borders and a stop to and and all deportations.
I don't think any party who openly works with the AfD could be called moderate.
But yeah, on paper they don't sound too bad (ignoring their pro-russia sentiments)