He's referring to native apps in general, not just Youtube. And I agree with him. That's one thing I like about Android. Don't need a system wide update to update a specific native app.
And yes, while Apple can release a small update just to update an app individually, they've almost opted to update native apps in conjunction with major OS updates which only occur once a year. (2.x to 3.x, 3.x to 4.x, and so on.)
Apple rolls out updates to iOS and its native apps as fast (or faster than) most developers release updates for their apps. Since September, they've released 4 minor updates and 1 major. There are popular third party apps that haven't seen an update in months.
Anyways, I don't think most people care if native app updates come from system wide updates or not - an update is an update. It's more important that they are timely and installed rapidly by users.
iOS 6.1.2 is already the most installed version of iOS in NA, and it was only released a week ago. Not only are the majority using the latest version of iOS, but the majority also have the latest version of Maps and Siri, for example, because of it.
That would be very difficult to do for Android, but wouldn't it be great if 40% of Android users were running stock 4.2.2 and had the most up to date version of Google Maps, YouTube, Gmail, etc. Instead, the majority is running a fork of Android that's a generation or two behind, supported only by the device manufacture, and issued only through a carrier. Is it no wonder that native apps are updated separately, otherwise development would have been stuck many years ago.