All of them involve being a single person in a huge organization, which is very different from being (for example) the CTO of a lifestyle business or the first hacker of a startup.

A friend of mine works on CSS optimization at Facebook. That is both narrower and deeper than anything you would do at a small company.

There's also the question of who your coworkers are. Large companies are large enough that you can spend all your work time with other devs. That's not true at a small company.