"Full-stack" was never a reference to the OSI model.

You can spend your whole career deep in the layer 7 weeds nowadays. A legit "full-stack" technologist will dive into layers 6 and 5 occasionally.

Below that you're talking about TCP/IP, BGP, Ethernet, and fiber. The beauty of the model is that each layer doesn't have to care about the implementation details of other layers, and that's reflected in hiring as well.

Nomenclature aside, some of us really do span layers 1-7. But layer 1 is pretty boring, and there's not a lot of value to add in layers 2-4 honestly, except in extraordinarily demanding environments.

Even the people who think they work at layers 3 and 4 are usually just using layer 7 tools to manipulate configurations for layers 3 and 4.

Its how I perceive it - if you cant design an implement a full 7 layer stack for simple applications (ie CCNA level) you should GTFO

"The beauty of the model is that each layer doesn't have to care about the implementation details of other layers"

Err having worked on international OSI interconnects id take that statement with a bucket of Salt -)