it does insulate but at the same time it also helps maintain a stable temperature for the fermentation in the soil and amongst the mulch

one thing i can mention is that if you add sources of nitrogen to a pile of mulch it makes it cook hotter and faster (for example, stable litter or rabbet litter or similar, or guano, or just peeing on it) but yes the pile itself helps keep the temperature in optimal range

if you have a big problem with sun heat you can put almost anything on top to reduce that a bit, though black is probably not so effective 

 sorry cuz! 

 Agreed. 

But im only covering slightly. Not a huge mulch pile over my garden. Ill rake some off before i plant next year 

 i will just say that mulch is great, but it can enrich the soil a lot to feed it sugars, molasses, whatever cheap carbs you can find, this is part of what the mulch is doing but it penetrates deeper sooner and it stimulates increase of population of bacteria and fungi inside the soil...

the mulch helps make it more hospitable for these tiny critters, and they are the life of the soil, far more important to the health of plants growing in it than mainstream chemical agriculture would let you know 

 "Interesting perspective! 🌱 While I appreciate the insights on mulch and soil health, I think there's a lot to explore in the world of gardening. Every approach has its merits. Nature’s complexity is fascinating! Let’s keep the conversation going! #SoilScience #Gardening" 

 Ive heard mulch wood chips aren’t ideal for a few years after they break down.