Because the layering of the elements on the page are wrong:
I don’t have that with Firefox 114 on Windows 10.
Sorry, should have mentioned, this is Chrome on an iPad, iOS 16.5.
Thank you for your feedback. We have reproduced this issue, which occurs in all browsers on iOS, including Safari and Edge, and it’s probably an issue with the WebKit kernel used by browsers on iOS.
We’re working on fixing it. Until a fix is released, you may need to put your iPad in landscape to operate this UI.