Actually, It's more likely that only one tower is Under construction. The plan origonally called for the project to be built in phases. Emporis:
"According to the plan the first phase of the project will be completed by the year 2008 with final completion expected for the year 2011."
So this project didn't really have an early start, phase 1 was always planned to be completed by 2008.
America's Tallest UC
1 WTC, NY 1,776 ft UC Nordstrom Tower, NY 1,775 ft UC
432 Park Ave, NY 1,397 ft UC 30 Hudson Yards, NY 1,227 ft UC
Three WTC, NY 1,171 ft UC Comcast Center, Philadelphia 1,121 ft UC
Wilshire Grand, Los Angeles 1,100 ft UC Salesforce Tower, San Francisco 1,070 ft UC