Is the far right Austrian "Freedom" Party taking votes from the center-left?

A quick take from Anton Pelinka, who seems to be theAustrian political scientist most quoted in the press, on whether the far-right Freedom Party (FPÖ) is taking votes that would otherwise go to the Social Democratic Party (SPÖ).

He seems to argue at least for the 2017 national election that it's not a significant number (Vorwärts-was sonst? Die Zeit 27.09.2018), "Most of the workers who voted for the [FPÖ] in 2017 were never SPÖ voters." ("Die meisten der Arbeiterinnen und Arbeiter, die 2017 die Freiheitlichen gewählt haben, waren nie SPÖ-Wahler.")

But he doesn't elaborate. And his comment as formulated doesn't address how many 2017 FPÖ voters were potentially swing voters open to the SPÖ.