Delta debugging is not new: https://en.wikipedia.org/wiki/Delta_debugging
My implementation of delta debugging, "delta" is 19+ years old: https://github.com/dsw/delta
I released it as Open Source because Microsoft Research sent someone to my office to ask me to, back when Microsoft was calling Open Source a "cancer".
The LLVM introduction by Latner refers to the "standard delta debugging tool", so it is rather well-known: https://aosabook.org/en/v1/llvm.html 'unlike the standard "delta" command line tool.'
For other readers' benefit: C-Reduce is a little more sophisticated than plain delta-debugging. From the abstract of Test-Case Reduction for C Compiler Bugs (2012):
> [...] [C-Reduce] produces outputs that are, on average, more than 25 times smaller than those produced by our other reducers or by the existing reducer that is most commonly used by compiler developers. We conclude that effective program reduction requires more than straightforward delta debugging.
(Of course, this means that C-Reduce is 12 years old now.)
At the same time, C-Reduce seems to be more general than the LLVM tool you linked ("BugPoint", dating to 2002), since that one works with LLVM IR specifically.
I think most developers are generally unfamiliar with automatic test case minimization tools and techniques, so the post may be helpful even if the ideas have been known in their respective circles for quite some time.