You're missing something, but that's sorta the point. The idea of what a full-stack developer or back-end engineer or hacker (or whatever term we want to bandy about)
looks like is largely based on stereotyping and a bit of myth. You can't tell what someone does for a living just by looking at them
all of the time, but you can
some of the time, so it's easy to play on that by dressing the part because we humans can be easily tricked into trusting our own information by default. If you cosplay as a network engineer, it's pretty likely that's what most people will think you do.
Say you're red teaming, and you are on-site looking to gain access to the server closet of a business. Some initial setup about you being there comes into play, but once there, it's up to you to look like you belong there, when some unwitting person with access to the server closet will lead you to it, then leave you to do your thing on the pleasant notion that you'll have the "problem" fixed by the end of the day. This is an ultra-simple scenario used as an example, but looking the part sometimes means having some stickers on your laptop that tell people you're really into a specific language or tool chain, or that you've been in the SOC trenches long enough to know what a lot of those inside jokes mean. Details often sell the lie.