Hard pill to swallow:

If you get hired as a full stack dev and then complain that you're doing 3 people's (or more) jobs while getting paid for 1,

You had it coming.

I disagree. Different tasks and volume of tasks are different things. Of course the likelihood does increase when you have more stakeholders or responsibility. That is why it's also very common with full stack Devs.

A good size team of full stack Devs or a team that is supplemented with one can really help making more cohesive solutions and better communication.

Same goes if your job title says IT or Dev.