Things the documentation doesn't make quite clear - Part 78

So yeah, per the AWS ECR docs, EC2 stores your images in S3.  What they don't tell you, unless you really go hunting, is that

1. This isn't just a feature, but something really relevant to you because
2.  You'll need to be able to get to S3 to push/pull image

Which may not matter till you, till you end up spending five hours trying to figure out WhyTF your wholly private VPC can't pull images from ECR.
Oh yes, you got the NAT gateway set up, and can do pretty much everything else (including pulling from DockerHub), but not from ECR.
Sigh.
It's good to know that the quality of missing information in AWS Documentation remains as high as it used to be.


P.S. The fix is easy - a VPCE.  But that's once you know the answer...