People within Eminence have said the drivers haven't changed in the past few years, that it's the way they've tested them that's changed. That is definitely possible, since electro-mechanical parameters shift depending on power level. I'm not just talking about increases in Re at high power either, there is pretty significant movement in electro-mechanical parameters as drive level changed, even at low to medium power levels.

Fortunately, π Speakers are slightly overdamped by design, and that makes them fairly tolerant of T/S shifts. Because of this, small electro-mechanical changes due to manufacturing tolerance, power levels or environmental conditions are a non-issue. The DI-matched two-ways are sensitive to cone and cap material and shape though, so if they change those then performance may be affected.