It'll be fine
If you're worried about the soil getting too hot, and the sticks in the medium are getting really hot, thats good because it'll keep the soil beneath it cooler as its taking the bulk of the heat.
Incidentally, I use MG "Expand N Gro" for my indoor grows, but would certainly use it for outside too if I ever did grow outside.
Its got zero peat, with the attributes coming from other fibrous biomatter, however its not at all full of big sticks like the others. It expands to 3 times its original volume when mixed with the same weight in water, so the soil is quite light/airy compared to many composts by nature. Even outside, I'd probably still mix in 10-20% vermiculite anyway, although thats less important outside. Also slow release nutrients which is good, and because they're contained in small balls in the soil, if you found your first batch was 'hot', you could remove them from your next mix, or reduce the numbers etc. That way you can tweak the strength of the MG nutrients.
Sorry just thinking aloud.