Here in the US people use liberal and left interchangeably out of ignorance. But the liberals being referenced in this story understand that they are not left wing which is why they refer to themselves as "centrists." Demsocs are to their left. Demsocs might be to your right, but demsocs are definitely left wing in the context of US politics. We have established over and over again that to more radical people such as yourself, demsocs are "just liberals" and not left wing. That's fine, that's your perspective. The liberals who call themselves centrists have a different perspective, and theirs is far more common in US politics than yours, and therefore it is very relevant to anyone who cares about what's happening in US politics.