Yep, the situation has changed since the post was made. Parent comment was correct at the time, however.
At 5:40am Eastern, the agent at my departure gate told us that there was a ground stop affecting all flights, which was reflected in my original title. This was not reflected in the NOTAM I posted, as was pointed out by several early commenters, and in fact my flight was able to board and depart around 7:00am Eastern before the ground stop took effect.
https://www.bbc.co.uk/news/world-us-canada-64236047