Thus, if you were wide open some "entrepreneuring" company comes along, replicate it, and gain the first-to-market boost, while you are still trying to finish.
With a "stealth mode," a company can make a polished product and spring it on the market all at once, leaving no time for half-assed copies.
So, I'd say it upholds the thought that it's about execution, not the idea. The stealth enables you to release better execution without competitive pressure to release.