Mash and crumbles are pretty much the same thing and bigger particles than the starter feeds. They are usually made through a heat process that makes them "extruded", and they are more porous. I've never used starter, but I'll bet the crumbles absorb much more quickly and therefore clump better. I know the laying mash I use clumps better than any scooping litter I've used.
Laying mash, laying crumbles, layers mash --- all names for feed intended for egg-laying hens.
Normally, the only livestock feeds that are medicated are for young, growing stock (starter or starter/grower feeds). Because of USDA requirements, food animals can't be given antibiotics within so many weeks of slaughter. The same would apply to laying hens, because the eggs must be antibiotic-free.
Before you criticize someone, you should walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes.