NoCheat? I could have sworn IDP itself added the LOS checks. Even so, NoCheat is very easily customized, you can not only disable certain checks, but change what it does when one fails, for example kick, warn, nothing, etc.. If it is the IDP LOS check that I'm thinking about, then the problem is that it treats all blocks that are not on the exception list as full blocks. This could be fixed with perhaps 'Partial Blocks', something that would allow certain blocks to ignore LOS checks on some faces, for example repeaters on the top face, where there is mostly air.
The reason line of site checks were added is to prevent players from accessing chests/waypoints/levers that are on the other side of walls. This can be done via hacks, or by breaking a block and trying to interact with the lever/chest/etc on the other side before the block re-appears, playing with other peoples levers isn't cool!
Ahem.. speaking from a completely outside point of view here.. because after all, I am not Nosliw