Maybe this isn't dumb, maybe its me, but if he never trialled how do they know he's too slow? And 3 rides doesn't make a good second horse IMO.
And honestly a lot of STBs are usually rather quiet. 3 rides and a good mind wouldn't be that bad of a second horse for an experienced rider. I love standies. They make great pleasure horses. I worked as a groom for a couple different STB trainers. I did a lot of jogging and training with them. I actually am looking at one now that I am going to take from the track. He never even made it to a Q race. He was just to slow, so I am taking him from the track and putting some rides on him and he will be for one of my clients kids. He is so quiet, loveable and as close to bombproof as a horse can be. So as long as this continues when I get him under saddle I think he is going to be a great kids horse.
Anyway i'll shush now. I