proxy.config.http2.active_timeout_in is added by TS-4162. The default value is 0 for compatibility with existing 6.x code.
We're going to choose suitable value and set it in 7.0.0
☂ Critical issues for v7.0.0 release
Http2ClientSession close connection by INACTIVITY_TIMEOUT event, even if the connection is still active
GitHub Pull Request #917