The problem has to be determined to be caused by the wastegates. I wouldn't make a determination on whether or not to get an extended warranty based on the SIB.
Anybody who has owned their car from new knows, that BMWNA gets into semantics when it comes to determining coverage, and that's with a full factory warranty.
Who wants to get into whether or not their turbo needs replacement due to a wastegate, or something else? the person with a problem just wants it replaced period. my .02.....