I was searching for filenames that contain the word "leadersh" and the results were random and unexpected. Not sure if it is a bug or something else.
Directory Opus Pro 12.24 Build 7795 x64
OS 10.0 (B:19043 P:2 T:1) SP 0.0
Those are the real filenames within the recycle bin.
Shouldn't the search results be files with the word "leadersh" in their name?
You're using the Windows Search field there, so what happens is entirely up to Windows Search. Opus just passes the search query through to it and displays the list of results it sends back. It may be searching file contents or other properties (e.g. Display Names of the recycle bin items, which are different to their real file names.)
You can use Tools > Find Files to use Opus's own search/find functionality, which should behave differently.