My understanding is that covers aren't fair use since they're derivative work. Getting a mechanical license allows you to publish and sell covers, where a sync license allows you to do the same for videos. At the end of the day, every company's terms of use varies though
From what I understand, cover VIDEOS require a sync license, which are apparently nigh impossible to find. What's a VGM cover musician to do when he wants to cover a song, and put a video of it on YouTube (unmonetized) as a way to build a fanbase?