"That's... a little vague. But it's more definitive than the time frame offered to anyone waiting for the Creators Update on Windows Phone. That isn't going to roll out until April 25, and Microsoft carefully noted that "update availability may vary by manufacturer, model, country or region, mobile operator or service provider, specific installed software, hardware limitations and other factors such as feedback from customers." How reassuring!"
1) Staggered rollouts are normal. They often stagger major releases regardless of whether you're talking about PCs, phones, or a console. Not news.
2) They're covering their butts, in cases of factors outside of their control, or if they run into issues. If there's a delay... it's software, man. Think of it like game development, but bigger and more vital to your system.
With that in mind, they've said the same things in past updates and I've never had an issue bypassing my carrier and getting the update around the release date.