They began excavation for this and Parade in unison, back when Montage was still being excavated, I believe, so it's had a big head start. The excavation itself must have also been significantly easier than other projects in general since they really only had to dig out space for three walls while the fourth wall facing the tracks is already fully exposed.
That, plus this project hasn't been receiving the same wealth of coverage as in threads for other projects.
Still, it does seem to have risen extremely fast.