This seems to be at odds with the constant complaint of a talent shortage, especially when startups have to compete with the offers made by AmaGooBookSoft. Which is to be believed?
If the company values you and you hold the keys to some aspect of the company's operation, the team is far too small for them to practice poor retention.
On the other hand, with a finite runway and the need to move quickly, if you can't keep up, there's little reason why the company needs to have you on board.
So I suppose it cuts both ways... but if you're a competent employee, I see startup hiring as advantageous for the employee at this point in time.
Startups also do experience a higher degree (usually mutually agreed upon or voluntary) personnel turnover, some time well into the later stages. If you don't expect it, it can be unnerving: imagine if the person who recruited you and who you were eager to work with quits (this really shook me up first time it happened!). Nonetheless it is actually healthy: if someone believes that their personal interests and the startup's interests no longer align (either they don't think it will be as successful as they hope, or it has changed direction in a way that their technical skills are now underutilized), it is better for them to depart.
I think the article is mostly right. One place where I will disagree is in regards to "risk": traditional corporate careers (think joining GE or IBM and staying there for 10-15 years, entering management as the only possible promotion) actually offer less job security than working for younger technology companies (whether startups or Google/Facebook).
What one should consider instead are opportunity costs: financial (a startup might match a bigger company in base pay, but they will usually not offer RSUs that you can start selling in a year), but most importantly the non-financial ones (if the startup fails, will I still learn any unique, useful, and broadly applicable skills?)