Any context where network things don't work like they should. This would include why your home internet is 'flakey', why your load balancer doesn't quite balance loads, why some database connections are slow but others are fine. You may not need those skill but busting out tcpdump and looking at pcaps in wireshark is part of calling yourself full-stack.

With the cloud it may not matter as much if you've never twiddled SACK settings, but there's a large body of knowledge that is entailed by full-stack that can't be covered in boot camp.