I have just stumbled on
this recently updated page about Chicago skyscrapers, which indicates Parcel I's height as "984ft+ (300m+)". Of course that got me excited, but then I realized this is most likely just speculation based on the same diagram that we have seen, as the author continues to write:
"The proposed height for the tower is 950 ft, but it’s highly likely that the figure is not measured from the ground level, but from an elevated position atop the parking podium at the bottom of the tower, so the actual height could surpass 984 feet and make it a supertall tower. The tower will be purely for residential use, offering 600 units. The development was approved in 2018, and the construction could begin in 2022."