This can be achieved with only two Flows and no Countdown Timer required. I have been running this for a few weeks in my laundry and it has yet to fail (the light stays on when required for as long a someone is in the laundry and turns off soon after).
To achieve this without the Countdown Timer, we simply need to adjust one setting in the Z-Wave MultiSensor…
Adjust the Motion Alarm Cancellation setting to how long you would like the light to turn off since motion was last detected.
Note: The image above shows the settings for the Aeotec MultiSensor 6 - This setting is also available for the Fibaro Motion Sensor - however at the time of writing this there is a known issue saving setting changes with this module (I have been assured this will be addressed in V2 release).
The two Flows are then very simple…
One to turn on the light (for me, only if the Lux is below a certain threshold - so it does not turn on when it isn’t needed)…
And another Flow to turn the light off (once the Motion Alarm Cancellation time has expired)…
The Motion Alarm Cancellation will reset itself when motion is re-triggered (this is why we don’t need the Countdown Timer).
Now I am in no way suggesting this is the “best” way to achieve this scenario, it’s just another take on a possible solution to the same problem 
One of the things I love about Homey is the fact there are always different ways to achieve the desired result!
I hope this helps 
