Idk, that is terrible advice. I've known several people who got hired because they emailed the CEO of 5-20 person startups.

Heck my CEO asks me all the time that people are messaging him and if i think they are interesting enough to hire.

If it's 5 person company they likely don't have HR or recruiting and the CEO is likely doing the hiring (for VPs/Directors/etc). In that case of course you would communicate with them directly, they are effectively a hiring manager and don't have HR to outsource the hiring to.

If the company has a person/group dedicated to hiring then going around them is counterproductive. IMHO of course!

Agreed. I've worked in startups most of my career, I've messaged CEO's, CEO's have been messaged, never a negative experience and higher quality candidates in my opinion.

Side note: You gotta hustle people!