They are magnetized to set values, though, right? That's the last step in manufacture. They aren't set at a specific Henries reading from then moment they are cast. The only question would be the upper bound.Here's a GITEC / PotEG chapter on that https://www.gitec-forum-eng.de/wp-content/uploads/2019/02/poteg-4-4-1-alnico-magnets.pdf
Long story short is that AlNiCo 2/3/4 are low magnetism, high permeability, while AlNiCo 5 is high magnetism, low permeability, and AlNiCo 7 and 8 are even more so, to the point of being more similar to ceramic magnets. The stronger the magnetic field, the more it pulls on the strings, which shifts energy from wider harmonic divisions into the narrower ones as well as increasing asymmetrical vibration, resulting in more treble and a chorus-like sound. The higher permeability just increases the inductance and shift the resonant peak down, as well as increasing the voltage output a bit, by improving the pickup's ability to receive the magnetic field back from the magnetized guitar string.
If ceramic is at one extreme, then steel is at the other; very very high permeability, virtually not much magnetic field of it's own, but it does have one. That's why steel pole pieces have to have some other magnet underneath. AlNiCo 2 is the most middle of the road in terms of having a formidable magnetic field and permeability.
I'm interested in the actual results in comparing magnets of the same strength but different materials - and then matching up those sonic results to the material qualities, which I understand you are laying out.