Well, if that was practice, then attackers would know about that. Also, there is possibility for someone who is running away to trip.
However, there is a hole in logic - what roof has any strategical advantage? Perhaps, one person will trip - rest of 99 out of 100, that are chasing you would eventually go through. Were there any further routes from the roof? Death from falling is my guess...
The reason why there would be higher step for roof, might have more something to do with dampness and to prevent wearing of that step, or to prevent leakage from the roof, that would stream down the stairs. SAeriously, who is making those stories, that makes no sense and who are so gullible to believe them? Are there any of those stairs seen on money? Drunks from my native town were telling stories about oak(which is recently planted - no more than 50 years), ythat they claimed were pictured on money... usually they wanted to claim that money after a story, if someone wanted to disprove it and brought their vallet out...
I think your mental model of a castle is not quite correct. It's not necessarily a simple stone box. A lot of roofs lead to higher points, or to walls.
Your mental model of what can happen in a castle is also not complete. It's not just sieges, there are any number of reasons someone could be chasing you. It could just be one assailant.
Finally, perhaps I didn't describe the step well enough. The step is not the top one, it is the second one down, and the face of it is around 2cm higher than all the other steps. It wouldn't make any difference to the drainage. Don't get angry that there are features of castles that are not adequately explained, and some people try to explain them.
However, there is a hole in logic - what roof has any strategical advantage? Perhaps, one person will trip - rest of 99 out of 100, that are chasing you would eventually go through. Were there any further routes from the roof? Death from falling is my guess...
The reason why there would be higher step for roof, might have more something to do with dampness and to prevent wearing of that step, or to prevent leakage from the roof, that would stream down the stairs. SAeriously, who is making those stories, that makes no sense and who are so gullible to believe them? Are there any of those stairs seen on money? Drunks from my native town were telling stories about oak(which is recently planted - no more than 50 years), ythat they claimed were pictured on money... usually they wanted to claim that money after a story, if someone wanted to disprove it and brought their vallet out...