What is `x-ic-streaming-response`?

When I try to download a part of a HTML file:

curl -H 'range: 1-10' -v https://XXX.icp0.io/

I get

x-ic-streaming-response: false

What does it mean? Why isn’t it streamed? Why don’t I get only bytes 1-10, but the entire HTML? How to change to x-ic-streaming-response: true?

The asset canister does not support streaming yet. I plan to work on it soon