This was the first mention of it, specifically to let others know to set their union contracts to expire on the date that lines up with this.
Since union contracts are usually for multiple years, they need to let others know asap in order to coordinate that.
This also gives a lot of people that aren’t unionized yet, motivation and time to do so and set their first contracts to expire on the same date.
I’m sure they’ll ramp up and do most of the actual prep for this in 2027-2028. But if union workers in the next year were to continue to set their contracts to expire at different times of the year (as they have been previously), this wouldn’t be possible in 2028.
This is basically just a first announcement, using the publicity of their win, in order to inform and motivate others to properly coordinate and join.
Edit: my comment is in reply to echodot, but for some reason the reply feature isn’t working for me atm