They way high roosts can cause bumblefoot is that in heavy breeds, when they jump and land hard, the leg bones mash down HARD against the inside of the bottom of the foot, bruising it repeatedly. As the OP wrote, her birds carefully hop and step their way up the ladder, but when it comes time to come down, they never seem to realize they are not really good fliers and just take a crash dive off, in her case even so that they bang into the feeder, even though it has been there for years, and they have been crashing down for years. It is just chicken nature and they never learn. Repeatedly jumping down, especially if there is thin or no bedding where they land, causes damage over time to the bottom of the foot, the soft tissue and the bone at the bottom of the leg, Hematomas can set up a perfect scenario/environment for infection if even a tiny scratch happens nearby, the bacteria travel through the damaged tissue without defense, head for the damaged bones and set up camp, usually killing the bird eventually. Chickens have been greatly altered in size, weight, flyng ability, with usually the biggest and heaviest ones having lost the most of their flying ability over time, compared to game types that are much more flighty and agile. It is our responisbility to provide a supportive environment when we breed out natural traits and replace them with soft fluff instead of feathers, double or triple the weight, possibly a tenth of the smarts, lol. It isn't too much to ask for people to lower their roosts and maybe bed the floor deeper in shavings. It's not all froo froo and looks when people do. It's for a reason.