I don't get the ability to "drillthrough

I don't get the ability to "drillthrough" under a PP context (as opposed to a true SSAS cube context). In PP aren't you working with the data in both its raw (un-agg'd) detailed, sometimes summed forms, already? How are you drilling through, that concept only makes sense to me when you're looking at agg'd facts. What am I missing? Is it just a "snap-to all leaf" kind of label that just drops you to an all-leaf level of the current context of fact data? Am the only one really f-ing confused by the BISM and PP, and the we're-depricating-SSAS statements, and the no-we're-not-depricating-SSAS-because-that-will-make-the-MS-practitioners-mad statements, and other baffling statements? I can see adding capabilities beyond what a traditional cube can provide, but not if the goal is to undermine the whole current market and foundation of current implementers. Greater products (and companies) have gone to pot when your market is confused as to what you're offering. They need to keep it simple becauese obviously the Windows juggernaut will not be able to fund these misadvantures for too much longer. And miffing your most prominent practitioners by confusion and obfuscations are only going to make for more skiddish buyers and will scare current MS BI supporters away from the platform. Maybe they don't care because it's self-serve? Don't anyone tell me that there wasn't a technical way to extend a fundamental SSAS cube and provide backward compatibility. MS used to bend over backwards to keep prior technology working going forward...are they too arrogant, conceited, or lazy now?