Isn't there a possibility they were killed because the M5 Ultra is coming why waste memory on a M3 series Ultra or any other high memory Mac Studio computer when the next generation is coming within six months?
Possible, to be sure. But given that you could still buy the cheesegrater Mac Pro (with RAM and disk at 2019 prices, and a 2019 CPU at 2019 prices) right up to the week that the the M2 Ultra Mac Pro was announced, that would be something new. Not exactly an apples-to-apples comparison, to be sure, but still.