Tankies are authoritarians. They advocate for and defend centralized and/or entrenched power. At the same time they also advocate for economic nationalization. They believe the latter - “economically benevolent authoritarianism” - makes them leftist. It does not.

In reality, they are merely advocates of bog-standard extreme rightism… feudalism, monarchy, oligarchy, and the like. If your economy and industry is mostly or wholly owned by the state, but the state is run by an entrenched ruling class, then the economy and industry belong to the ruling class, NOT to the people.

One cannot be leftist and also advocate for consolidation or entrenchment of wealth or power… those are literally the defining traits of rightism.