The time will come when as a GM (or a player) you just want to call something a horse. You don’t want to call it by the name of a breed, or what it does, or whatever. It’s a horse. It’s probably a “mutt” horse and thus of no particular breed anyway. It’s just a horse!
And that’s OK! Look, we have all sorts of breed names for horses. We have stats for horses, and stronger or faster horses are going to be better than average horses. When you’re getting deep into cavalry battles, these types of details can be important. But guess what - It doesn’t always matter. Sometimes a horse is just a horse and not a Rairbridair heavy draft horse.
This is true of far more than just horses. There is a point at which all the details we seem to be including in everything we publish are in the way. We give our customers as much detail as we can cram into a book, but we do so hoping that GMs are not going to bother getting into that much detail with their players.
Case in point - The party is walking down the road and sees a farmer leaning on the fence. They say, “Which way to Rhum?” and the farmer points over his right shoulder. That should be the end of that encounter! The party does not need to know that Benjamin Mackersson is having trouble with his wife or that his children are now 38, 37 and 34, or that he enjoys fishing and rye whiskies. They don’t need to know that the horse in the field is his plow horse, or that he bought it six years ago for 80sc and a promise of six dozen eggs. Even if we put all of that in one of our books, don’t use it! It’s there in case the party comes down the road and says, “Our friend will die if you don’t sell us your horse right now so he can be raced to the nearest town.” Now the GM has an idea of what Ben thinks the horse is worth. Or if they say, “Hey, what’s your name?” “What do you do around here? We’re looking for someone willing to make us dinner for a gold coin - how good a cook is your wife?” OK, hopefully our level of detail makes more sense that that, but details are not always necessary.
There are different styles of play, and there are different players. Some role players want to know what the farmers are wearing, and some couldn’t care less that the farmers exist. Overdoing the detail is a mood killer! We’ve mentioned it before, but I will never forget the time (I was playing, not GMing), that upon arriving in town, the party wanted to go into the bar. We saw the sign with the beer mug and went in - or so we thought. The GM kept describing the door to us. We wanted to know our characters were inside drinking and flirting with barmaids and he kept telling us the dimensions of the door, what wood it was made of, how the bolts held it together. Don’t be that guy! Your players will never let you live it down, and the entire session that night was a mess.