Upload Thumbnail feature for video becomes active only after adding transcripts

Hello, Community!
Please, help with issue regarding Thumbnail for video block.

  1. Go to studio for some course → in unit click on Add new component and choose Video block

  2. In opened form (course-authoring MFE enabled) check Thumbnail - there’s “Select a video from your library to enable this feature” message

  3. Add video (link to Video URL field)

As result : Upload thumbnail button still inactive, it becomes active ONLY after adding Transcripts
Is it expected behavior?

Thanks in advance!