To me there is benefit for third party Dyna-Cabs with several factors that are more fundamental than indivisible and mix IRs:
- The overall cab, speaker, and mic selection
- The room's tone
- The cab's placement in the room, which will weigh heavily in the final capture
- The acoustic treatment of the room overall, which reflects the creator's knowledge and choices
- The mitigation, or lack thereof, of reflections around the cab and mic
- Which single speaker on a multi speaker cab the engineer chooses by ear
- Which mic the creator chooses, since different mics of the same model can sound different
- The mic pre used in the capture. Cliff wrote that he tried two different ones, but settled on (I think) his Neve, which had less mids.
- The creator's cables, which will affect the tone of the cab overall
- The power of the studio, which notably had an effect on how tube amps act in different rooms, and will affect where the engineer thinks the cab sounds best.
There may be other factors too that are not coming to mind, but I do think the craft of the person creating the IR does matter, even with DynaCabs. What I've listed above includes factors of active decision making by the engineer as well as just the effect of the gear itself, each part of which will affect the tone, including the power. And I think of the gear itself as a reflection of the knowledge, experience, and taste of the engineer.
Not to mention, two cabs of the same model might sound different, and it was the engineer's choice of which one sounded best that led finally to the capture.
I really do hope that for all DynaCab packs that a matching IR and a disclosure of the overall cab wattage (for calculating Speaker Thump) will be included.