Haproxy stats writes only after TCP connection is closed

I’m using ha proxy official docker image: haproxy:2.4.11-alpine3.15

Everything seems to work fine, but unfortunately seems statistic is not displayed correctly.

So if I have client with open connection till Haproxy it will show 0 bytes all day long, until my client will close connection.

Seems statistic is written only after TCP connection is closed. Is it a bug or feature?