Why are the value for Hosted Zone ID different for ELB and Route 53 Alias Target?

You can get the Hosted Zone ID of Elastic Load Balancing here: https://docs.aws.amazon.com/general/latest/gr/elb.html

In your case I can see that the Hosted Zone ID is the one for US West (Oregon) - us-west-2.

The docs are a little vague about this:

This value appears automatically based on the value that you selected or entered for Alias Target.

However, the Alias Hosted Zone ID is not the same as the Hosted Zone ID. To create an Alias record, you just need the Hosted Zoned ID. Check out some of the sample requests provided here. They all take a HostedZoneId parameter.

So for your use case, I think you can just ignore it. All you need to know is that the 'Hosted Zone ID' and an Alias record's 'Alias Hosted Zone ID' are not the same thing.