Sage Bambino regular backflush drip tray?

Hello!
Yesterday I bought an used Sage Bambino (regular, not Plus).

I don’t really know a lot about this machine, but I read through the manual and also searched the web about this thing and I still can’t seem to understand why is there a place for backflush in the drip tray?

There is no mentions about backflush function in the manual and also on the web everybody says that there is no backflush on the regular Bambino.

Also, no water has come out of that place (I have made 5 espresso shots and descaled it) so I am getting worried that something might be broken.

Is the water supposed to come out of there in some situations and I have got a defective unit or it is just a bad design and everything is okay with my espresso machine?

Thanks

by gupsters