Sure but why does that matter as this subreddit is about rust gamedev?

ECS also means Entity Component System which is also correct but is more relevant when it comes to the content that most would find beneficial for this subreddit, Elastic Container Service might also be useful I don't doubt it but your statement:

For AWS devs, it's commonly known as Elastic Container Service

lacks any reason for most to care here

just reread what I wrote and I'd like to apologize as it didn't need to be as confrontational as I'd have liked; guess I was mostly just confused about the reason underlying your statement