/usr/bin/wall fails to send message into terminal window

[phu9Suop]

which wall
/usr/bin/wall

If I send
wall -t 30 Do some mate-terminal testing now
to a terminal, the message blinks in the terminal title bar, but does not stay and is not readable therefore.
I have to add
wall -t 30 Do some mate-terminal testing now | sleep 30
to make it permanante for 30 seconds.
The bug is threefold :

1. It should be sent to the window and to all tabs.
2. It should not disappear after the timeout, but only block the prompt during the timeout.
3. It should be sent into the windows and stay there.

Please confirm and correct.