Yup. It's a known bug on this beta. Makes navigating YT arduous. Looks like the app is rendering the title bar on top of the UI for some reason. The tabs themselves also do not adhere to the UI tint setting. Kind of a train wreck.
I discovered that using per-site CSS to move webpages down works as a crude (ugly) workaround to the Safari “un-clickable top-bar” bug. Requires a Safari extension like Makeover.