I always thought Mike Clink was smart enough to know Slash was probably looking for a higher power sustain version of Robert Fripp's fuzzy max sustain 50s LP tone (example on this Eno track below)... so the Alnico Duncans made perfect sense to get this Fripp smooth power and sustain with more output and a little brighter
This Fripp tone is one of my favorite of all time
Tone at 1:47