Not sure, but the fact that IoK has apparently had to deal with militant activity should show that it's quite difficult maintaining even a sealed of border. Now imagine the Kashmir border only 100 times larger, even the US can't do it properly (Mexico-US border is a prime example).
Actually, that's where you're wrong too. Considering that India has to deal with border alleged border infiltration from militants quite a bit, proves how flawed your counter argument is. there is also the problem that you're argument is ignoring geography too. BD border is sealed with the help of BD, and so is Kashmir (along the LoC) with the help of Pakistan, but both borders aren't 100% secure (like some members here are trying to pretend it is), so again, your argument doesn't make sense.