Unless he was using prop throughout his test levels are probably still through the roof by now. That's why many advise to start PCT at least a week after the last jab, especially when using long estered test, deca, eq, tren enan, etc. Dont get me wrong, IGF is nothing short of a godsend, esp for PCT. But he surely isnt feeling the GH yet, not even close. I can understand the pumps from the IGF, but it does not increase strength, at least not as you're using it. So a lot of this is the placebo effect, as well as your buddy still having hi levels of AAS in his system.
As far as the decreased bf and increased vascularity, thats partly from the IGF and partly from him losing water from his cycle (assuming he's somewhat lean to begin with)