Maybe, but I think there is a market for 8.5 digit meters, and it's big money.
Well that’s the thing: I suspect it’s very much
not big money. Given that digital electronics have taken over so many things that used to be done with analog electronics, I would imagine that the need for ultra-precision multimeters is smaller than it once was.
So indeed, chances are the 2002 design reached its limits in terms of manufacturability, and that the new owners concluded that the market simply isn’t big enough to warrant the cost of developing a new one.
And let’s not forget that CERN developed its own open-source 8.5 digit meter, probably precisely to avoid having to buy hundreds of $$$$ 8.5 digit meters from Keithley, Keysight, or Fluke. (They wouldn’t have spent all the money to develop it if they only needed one or two units.) But that design is now out there for anyone who wants it, and it’s precisely the high-volume customers who might make more of those instead of buying COTS.