When a SO says "This stallion is not ideal for..."
Even though I don't plan to breed my mare (at least not for a while), I still enjoy looking at stallion owners' websites to see what the stallions on their roster are doing and producing.
I've noticed that many of them will have lists of things that the stallion tends to do, such as improve a hot mare's temperament, add bone and size, etc. Some also provide information on what the stallion is not ideal for, as in "this stallion would not be ideal for mares who have X characteristic", where X is usually a very specific conformational trait like a too short or too long neck, low heel, back at the knee, etc.
How do they come up with these lists? Is it simply from an analysis of every mare that is bred to that stallion and every foal that he throws? Or are the stallion owners taking other things into account?
In a couple of instances, I've found it hard to imagine that all the conformational non-idealities would have been represented by the collective group of mares coming in.