It already says it’s a presence sensor. Adding the capability to the device type is not going to change the battery usage.
There are many different ways to do presence sensors, and I don’t know how Iris does theirs, but SmartThings is really basic. It’s just counts the amount of time since the last check in. There’s no exit event.
Since all Zigbee devices check in occasionally it’s really just going to come down to whether the checks are often enough that SmartThings recognizes it is present.
You can change that parameter in the IDE somewhat, I don’t remember the exact settings.
But I’m pretty sure giving it that capability just tells SmartThings to track the check-in’s. Shouldn’t change the device behavior.