Static outbound IP addresses doesn't work with S3

1

Hello, so I have a Free app that is in Oregon region and it said I should whitelist these 3 IPs

100.20.92.101
44.225.181.72
44.227.217.144

And so I did, but the app can’t access to my S3 bucket with IP policy enabled. When checking the upload logs, I realized the actual IP that hit S3 service is 10.219.26.138 and I can’t find this IP anywhere. I’m afraid it’s not in the official document so just want to ask.

2

Tried another upload and I got 10.219.25.178 this time, I feel like this instance outbound doesn’t go through the load balancer?