Security patches are important to make sure the device is secure. You should not block these updates.
Since they are saying they are "rolling out" the updates, they probably haven't gotten to you yet. Sometimes it depends on serial number of your phone. or region you are in. It'll get to you eventually. I've experienced this with Unlocked Nexus and Pixel phones, they announce the update but they do it in phases. Patience!! :)
That's why Essentail has different builds, based on carrier (Sprint and Telus have a different build). https://www.essential.com/developer/current-builds
You can read some comments here also: https://www.reddit.com/r/essential/comments/7hrmck/essential_build_nmj51b_rolling_out_now_with/
On reddit, all poeple having this phone will Bell have received the update. But people with Sprint or Telus are wating.
There is no reason for Telus to block these updates.
The good thing about not getting updates immediately is if the update contains bugs then your stuck with the bugs which some can be a servere as making your device unusable and have from many of the major companies over the last few years. This is why they roll out in phases not all at once to prevent everyone from having messed up devices instead of a small batch.
The chances of being hit with an attack on a vulnerability that the update is going to patch is much less than getting an update that contains bugs so the trade off is worth it I'd say.
I was under the same situation as you with my Essential phone:
What I ended doing is getting a Prepaid SIM from another carrier and all the updates popped up as soon as it finished restarting. I actually just checked if the December security update is available with my Koodo sim and it is not, so I have to pop in by prepaid sim from the other carrier to have the update.
I wish the updates are available as they become available too.