It's interesting that the architect's website says
"At 65 stories and 262 meters (884 feet), 900 Albert will be the tallest building in the national capitol, anchoring the district on the skyline and creating a new visual link across the city."
Imagine if it was actually going to be 262? That would be only 10 metres shorter than Aura in Toronto, taller than Stantec in Edmonton, taller than anything in Calgary, even taller than the new 'tallest outside of Toronto' development in Burnaby.
The same page lists the shorter tower at 54 floors and the office tower at 27 floors however, so I would take it with a grain of salt. I think this plan went through many renditions before the final product that was approved.
https://www.gglo.com/project/900-albert/