At a mid-sized startup, the front end developers are probably also responsible for Django / Rails, and the back end developers are responsible for things like managing the Hadoop cluster and the machine learning components.
And at a large company, anything built with existing libraries might be considered front end, whereas back end might be creating a new database or whatever. I don't claim to know how Google works, but as companies get bigger the back end tends to go further back, and so the 'front end' encompasses more also.
They still hire frontend devs. Those frontend devs still do front-end JS with libraries. Some of them work on in-house libraries, but their focus is still narrow. Same for backend - they use the industry standard term to mean the industry standard.
However, the differentiation of teams/departments is much higher. To take on your argument directly, a project to create a new database would have software engineers but be on an infrastructure team. They don't call themselves backend engineers or recruit backend engineers, they call themselves software engineers and recruit people with skills writing system software.
You could easily end up with 'server side' work, which exists solely to augment or support a UI, and is not part of the 'core' business applications/services.
