You must remember that the info given on that website is old, & I believe much of it is "faked"--well, I shouldn't say that particular site, I'm not sure it's the same one, but there was one that used photos that had been "posed" by PETA.
We had many PMU farms in this area up until the contract cuts several years ago, and I have visited many of the barns. Years ago--and I'm talking 30 years?--there were not strict inspections and yes, some of the mares did have a rather sorry lot in life. In recent years, though, rules became much more stringent, and conditions in all barns were closely monitored.
If an inspector walked into a barn & saw a mare with sores, she was off the line immediately--and if he returned & found that mare was back on the line...the producer lost his contract on the spot. That's the way it is with all their rules, and no one gets away with keeping their mares in substandard conditions any more--and haven't for years now.
Quite honestly? In the past 20 years I've seen more abusive situations in "private" barns than I have in PMU barns. PMU barns have standards they must adhere to. Private barns have none--anything goes.
One fellow built a new PMU barn and had it all approved--the ceiling was the right height...then he poured the cement floor, and the inspector found that the concrete floor made the ceiling 4 inches lower than the height specified in the standard. He was told that he had to lift the ceiling at least 4 inches or lose his contract. Mind you, the ceiling as it was was still plenty high that it wasn't causing any hardship for the horses--but he still had to lift that ceiling.
tagalong is perfectly right. What she described is the standard, not the exception.