A repost is a pointer, not an upload
When someone reposts, TikTok does not copy the video onto their profile. It records that they shared it and keeps serving the original author's file. That is why the download you get is identical to what you would pull from the creator's own page, and why deleting the original makes the repost vanish from the tab too. Nothing about the sharing account changes the file.
The tab can be turned off
Reposts are public by default but the setting can be changed, and some accounts keep the tab hidden. An empty result means either nothing has been reposted or the profile chose not to show it, and the platform does not distinguish between the two from the outside. Trying a different profile is usually faster than waiting for one to open up.
Reposting is not the same as liking
A like is a private signal that may or may not be visible; a repost pushes the clip into other people's feeds and carries the sharer's name with it. Because of that, reposted content skews toward things people are comfortable endorsing publicly, which makes the tab a different kind of list from a Liked tab even for the same person.