I'm not sure what this means. C* and CM Fortran weren't particularly low-level, unless C or Fortran 90 are "significantly low-level". For low-level fun, you'd drop to Paris (or to CMIS for "breathtakingly heart-stoppingly low-level").
For the curious, a great archive of documentation for stuff that actually shipped is here: https://people.csail.mit.edu/bradley/cm5docs/
This reminds me of an interesting talk by David Beazley where he discuss the early days of Python, when IIRC he was a student at a national lab, and they managed to run the Python REPL in an connection machine 5 that people had a hard time programming in lower level languages. It seems the work they did back then, writing modules that allowed the Python interpreter to interoperate with scientific code was one of the foundations for it to snowball many years later.
So I wonder if what this paper describes had shipped in time, if that would lead us by butterfly effect into the alternative timeline where Lisp dominates scientific computing, instead of Python.
And as REPL for CERN libraries, instead of ROOT.
Unfortunately while Python has taken over Lisp's domain, we are still far from Lisp capabilities to generate native code.
EDIT: CMT docs are still around, https://twiki.cern.ch/twiki/bin/view/Main/LearningAthena