There can be different versions of the same driver group with different characteristics. Large orders can even specify variations. It's extremely unlikely that 2 units with a 13db difference in efficiency are using identical drivers regardless of the tune. It's fine to not know of these things but if so, it's better to not speculate. Your opinion on sound isn't hindered by any lack of technical knowledge. Assumptions are common and bad for headfi reviews. I also think a good review would also contain a full set of specifications. Efficiency and impedance are important ones for those with noisier, weak, or higher output impedance players for instance. Helps with why many read a review, personal viability.
This is more for people who aren't quite familiar with driver details:
It's important that people realize that while a W4 and 4.Ai can be using the 'same' drivers, drivers are not the same and efficiency will differ. Saying a driver is a DTEC tells you only these things: (1) they use the same drive mechanism i.e. U-shaped or L-shaped, and (2) they have the same front/back volume (unless it's of a vented variety). It does not tell you the coil impedance, phase, internal damping, integrated RC circuits, etc. Those are the things that influence crossover point. Two DTEC drivers may share the same general sound, but depending on the drive voltage, the passive electronic components attached (i.e. crossover), and acoustic dampers applied, they can respond very differently.