Was I thinking of the 310 with a 100 CI that used to descend so slowly?
As to who actually came up with the 290, I'd speculate that it was either JB or PC. But I don't know that for sure.
MG2
Dunno... Most folks are out of profile early and if you don't look at the box, you'll never know what it wanted to do. Or the 290 is in, modifying the box, so who knows what it wanted. But been mostly on the late side so noticed that it wants the higher speed.