That's because hobbling camels was the normal procedure when camel-mounted troops dismounted, to stop them running away.
When cavalry dismounted, they usually had horse-holders (one for every four horses or so), and the horses stood. Using kneeling horses as cover is very unusual, something I've only ever seen in Hollywood westerns. It's very rare that manufacturers even give us horse-holders or dismounted versions of the troopers for our cavalry (and dismounting to fight was pretty common towards the end of the century), so there is no reason to expect they would produce a figure of something that almost never happened.