I work in FinTech and trading systems - very high performance and low latency systems. I deal with databases and huge amounts of data too. And I've (as well as coworkers) have hacked together trading GUIs and simple CGI to throw together data visualizations. But none of us would ever call ourselves full-stack and we'd never hire a front-end person who thought they were going to go mucking around the infrastructure. They just aren't good enough. This goes equally to small startup like firms I've been a part of as well as banks.
From what I've seen "full stack" seems to be entirely a web notion. Is it just that the backends are simpler - requiring little more than glueing together some Spring components for CRUD operations?
It seems to be a very new concept.