The article is mainly about revenue growth, and any startup should be willing to share top line revenue and growth rate.
A large reason not to share things is some info is sensitive, for example the share count is a useful number, while the full cap table with each investor’s pricing, terms, and contact info, and other employee grants, would be sensitive and might be more guarded. Same thing about total revenue versus the customer list.
More traditional advice is to ask about the fully diluted share count, so you can see what percentage the options would be, and of course the vesting schedule and purchase terms. Also I’d also ask about cash or runway, which is related to the ability to survive a rough patch.
I was CEO and founder of a YC funded startup and have some experience hiring at the seed stage. For me personally, I wanted engaged people and asking good questions was a positive sign.
That depends on what the company is looking for in you. If you're going to do mission critical stuff or they want you for an important role they might even enjoy showing you their internals. And if they don't want to show you then that's a pretty good indication that you are probably better off elsewhere. Transparency in an early stage start-up is good for everybody, including the founders. If founders are not willing to share their position they are effectively asking you to buy a cat in a bag.
No private company I have ever worked for as an employee has agreed to let me look at their balance sheet or income statement. Most would not even discuss valuation in terms other than # of shares in my offer, which is meaningless.
One CEO I recall even laughed when I asked at the interview (that should have been a red flag in retrospect). I later learned he gossiped about how inappropriate it was for a candidate to ask about company financials.
I have asked several companies about financials and they never gave any meaningful information. I got the impression that as an employee you aren't supposed to ask any questions. This is acceptable only for investors and upper management.
The companies who were open were the ones who options/shares became worth something from personal experience. The ones who hide those details had worthless options.
Honest question; seems like it's a tougher thing to get access to than for a VC, but maybe I'm wrong.