What you're referring to are usually called sponsored segments. They're ads, but they're just a part of the video file you're being served. They're not dynamically targeted or cycled out. So if a LTT video is sponsored by ASUS, every viewer will see the same sponsored bit about ASUS because as far as youtube knows, it's a genuine part of your video, not a slot for an ad bid.
They're still annoying, but it's not a pre-roll ad. You don't get those with Premium.