about pg14 new parameter in_hot_standby

in the pg14 document(https://www.postgresql.org/docs/14/runtime-config-preset.html)

in_hot_standby parameter:

Reports whether the server is currently in hot standby mode. 

When this is on, all transactions are forced to be read-only. 

Within a session, this can change only if the server is promoted to be primary. See Section 27.4 for more information.

"Within a session, this can change only if the server is promoted to be primary"--- I can not understand this statement.

I think document will tell us:

when the postgresql cluster is in the standby database role, the standby database parameter in_hot_standby value will change to on，and this in_hot_standby parameter can not been modified in the session.

I do not know what I say is correct or not.