I don't have any other 670s, and I've never used a real one, but IK claims a spot-on emulation based on an actual vintage unit.
I've had the IK 670 since they put it on sale some years ago. All I knew at the time was that the Fairchild had been the default compressor at EMI during the Beatles era, and that they'd used it on
everything.
At the time I'd been looking for a vocal leveler, but as it turned out I already had other compressors that did that job better, so the 670 has been languishing ever since.
For M/S compression and widening, I normally use Pro-C. Although it's not capable of the short attack times the 670 can do, I have 1176 emulations for that and it's rare to need a 200us attack
and M/S at the same time. But your demonstration has inspired me to revisit the 670 and give it another chance.