Issue in the example of logical replication

Hello,
I have looked at the examples provided, and a line is unclear to me.
https://github.com/jackc/pglogrepl/blob/master/example/pglogrepl_demo/main.go#L129

Whenever we receive a keep-alive message, we move the client's WAL position to the current end of WAL on the server.
This does not seem right.
Could you please comment on that? Maybe I am missing something.

Thanks in advance.

Read example/pglogrepl_demo/main.go at line 129 and check the PostgreSQL logical replication semantics for keep-alive messages. Determine whether advancing the client WAL position to the server's current end is correct, then clarify the example or identify the needed change.

Written by the indexing model from the issue text.