"Send & Close" don't respect the "Send cancellation period" (to Undo)

The “Send & Close” button is not respecting the “Undo” timeout configured in Gmail.

Gmail configuration:

Example: The Undo pop-up is displayed only during a few senconds (5 sec.?) even of the “Send cancellation period is set to 20 seconds”.

Is it possible to have the “Undo” feature working properly with the “Send & Close” button?

Thank you

Kind regards,

Borja.