Seated keyboard able to send input to application running on different seat

I have a setup with two seats (seat1, seat2) using the kiosk shell. seat1 has a touchscreen as input and one display as output. seat2 has a touchscreen, keyboard as input and one display as output. An app runs on each ouput and they are launched at startup. Because the app that runs on seat1 is launched second, it gets keyboard focus from the keyboard assigned to seat2. This behavior seems undesirable to me.

I would expect that if I assign a keyboard to an output it would be locked to the output the way the mouse is locked to an output, at least for the kiosk shell. To fix this there should be a check when keyboard focus is set to ensure the application is on an output assigned to the same seat. Also, when an application moves between outputs, keyboard focus should be re-evaluated to ensure it stays locked to a monitor.

I have implemented a hacky fix for my case but a real fix for this issue would be appreciated.