"Serverless" isn't a misnomer. It's the movement of management of everything below some API and/or Runtime to outside of your organization.
A technology can enable a serverless culture within an organization, but that doesn't mean every deployment of a so-called "serverless" technology is actually serverless. If I write a lambda function, but then my ops team deploys it on a piece of metal running in their closet, its not serverless. Inversely, I can write a traditional stateful NodeJS app and give it to Heroku, and it becomes Serverless.
In that sense, Serverless isn't really a quality of the technology, though certain technologies are optimized to be serverless. Its a quality of how its deployed, and more importantly your organizational culture around that. Of course, technologists hate this definition because we can't just call whatever we want Serverless. Moreover, Serverless starts seeming a lot less like the desired end-state we should aim for; often it makes sense to manage your own servers, just like it sometimes makes sense to manage your own hardware.
OpenFaaS can totally be serverless. But to qualify, we'd have to be talking about an underlying Kubernetes infrastructure that abstracts the metal and OS away, so something like Fargate or Azure Containers. Certainly not on DigitalOcean. Here's the signal: If I can SSH into something within the stack, it's not Serverless.