Only certain types of boost additives were for 30k+, and would damage engines below this alt. Unlike the horrible modeling in Ubisoft games, it would NOT blow your engine up in a matter of 2 seconds.
However, these planes had OTHER types of boost for below that 30k alt minimum. So below 30K you might use MW50. I'll use the german equivelant because the only thing I can think of that matches your description is GM-1, another german additive.
So up to and above 30K you can use MW50 just fine. Above 30K you can also choose to use GM-1.
AH just has it so that whatever that boost is at whatever that alt, you just hit the 1 button for it. You may note this also applies to takeoff power settings at low altitudes. They are enabled in the WEP power rating but then fall off above that to normal WEP settings, as in the real deal.
So it's all covered. Now, GM-1 systems are rare. Only one plane in this game has it, and there's some debate as to whether it's modeled at all on that plane or not. That plane is the Ta-152H.
No other plane in game sports this option, though they do have higher RPMs, higher MAP, water additives, MW50, and so forth.
All of those are added under the one simple key press WEP command.
