I don’t know much but I think with this extension you can decide the time for which the user devices’ screen will remain ‘ON’ and bright, whereas with built-in Keep Screen On property, it is not possible to assign the time @bodymindpower
Consider here the Auto Screen-off feature/setting which every device have in the devices’ setting menu. In this we are able to select the screen ‘ON’ period by selecting the desired time (15 sec, 30 sec, 1 min, etc).
Now if a user wants to perform similar task then he/she would just have to pass the time in the form of millisec parameter with this extension if he/she is using one.
Now to perform same thing without this extension(with Keep Screen On property) will require an extra clock component I guess along with other related blocks.
So this extension may save some blocks.
No-doubt that the mentioned task can be performed without extension but its just that this extension makes the process somewhat easier. This is what I understood, but the developer can clarify more on this.
I will say @Vaibhav explained everything but to make things more easier I will explain more In simple words.
Suppose user has set its device screen timeout to 15 sec. Now if you set the built-in Keep Screen On to True than the screen timeout of that user will be Never/Always but if you set built-in Keep Screen On to False the screen timeout will again get back to 15 sec but with this extension you can set the screen timeout to your desired time let, say to 1 min, 30 min, 15 min, etc. But you will have to pass the time in Milli Sec and with this extension you can also set screen time out to never/always.
Also after editing/modifying the user screen timeout time if you want to set it back as before you can also do that.