Doesn't matter.. Even if he would, most low level stuff would be almost equal (like the assembly generated) or at least very similar. Yes both are different compilers and do some things different (vtables/stack layout for instance if I remember correctly), but in the end if you know how the assembly generated from one works you'll have no problem understanding the other one. Besides, the screenshots from VS's mixed source/asm debugging do look nice and are really clear and helpfu for beginners.

He's a game developer. MSVC++ compiler and Visual Studio are (almost) a gaming industry standard.