A small company like that likely won’t have policies and processes to fall back on. This can be good for some things, but when things go bad it can backfire.

Mainly for things like promotions, HR, complaints, etc. In big companies there’s a formal process for how to get promoted and what’s expected at each level, etc. Same for HR complaints. At a small company you’re going to be more subject to the whims of whoever is in charge.

Same for new projects. In a big company you have red tape and processes to blame when something fails, but in a small company it’ll be more likely to be “your fault”.