"the landlord doesn't need to know you are claiming, that's the point."
If you lose your job while housed, then you can get away without telling your LL.
However if you need to find a new place it's very, very difficult indeed, as your new landlord will ask where you are employed, and many lettings agents won't even consider you.
I helped a friend on HB flat-hunt this year in London. It took him months to find somewhere (which meant he overstayed past the date his landlord had asked him to leave), he faced rejection after rejection simply because he was on HB. Another friend rented him a room in the end, but that was only temporary (while they were renovating their house). He'll be in the same position again very soon. Homelessness is a very real possibility.