Secret passage?

Playing through UnAngband recently looking at the level generation changes. One thing I've noticed is that there are a lot less stairs down than in other variants. I had thought the proliferation of downward stairs are to facilitate finding a quick way down as that is the more natural path for players, especially when 'word of recall' scrolls replace up stairs in the deeper levels. Without many stairs I find myself stair scumming (not in the truest sense of the word) for simple to explore dungeon that also contains a staircase down.

One dungeon I recently explored had only a couple of rooms and no obvious exits. As I was making my way back to the stairs to 'reset' the level I noticed something odd, a room with mossy granite walls also had a single slime covered wall to the south. "I wonder if that's the start of another passage?" I thought. Sure enough, searching around the slimed wall revealed a slimy passage leading to another room. Not sure whether it was intentional or not, but it stopped and made me think how cool that was. It was much more natural than blindly pressing 's' along each wall.