Well, SciPy depends heavily on NumPy, which as a CPython-specific extension won't run on other Python interpreters in general. Although for example there is ulab for MicroPython which replicates part of NumPy, and PyPy has a compatibility layer for CPython extensions.
Edit: well, Regessio itself also depends on NumPy, but might be able to run on top of ulab whereas I really doubt SciPy would.
Responding that there's something out there called ulab doesn't really answer my question, which was: where does op's requirement to not use scipy come from.
".. I had to generate confidence intervals on over 8000 univariate data sets using very small VMs, so I needed to limit large dependancies as much as I could. This package was the result of this!"
Based on the comments in this thread, it may be worth trying to make this package not dependant on Numpy as well?
Edit: well, Regessio itself also depends on NumPy, but might be able to run on top of ulab whereas I really doubt SciPy would.