I use 40% shea butter in one of my recipes and get those white dots like you wouldn't believe. I have never ever had them in recipes without shea butter. I've also experimented with using different percentages of shea butter and it makes no difference to the amount of white dots I get or their distribution.
However, I get noticeably more when I superfat 9% than when I SF 6% (my standard), both at 25% shea butter.
I now heat the rest of the oils up and pour them into my broken up shea butter chunks and let the heat from the other oils melt the SB. It takes longer and needs more mechanical effort, though.
One of the other reasons I believe in my experiments is that at too high a temperature, certain molecules can become denatured. SB is known to have unsaponifiables and these can consist of denatured components, that are unlikely to react normally with any other substance. So by heating up SB too much, it can cause more denaturing, creating more unsaponifiables, which may appear in the form of white spots.
Like when you overheat regular butter in the microwave, it becomes kinda 'textured' and will never return to its original butter-like state, even when cooled.
A lot of the above is speculation based on experiments and theory so someone please feel free to correct me.