He doesn’t look quite like a draft cross to me, and a TB can definitely be thick/as thick as the picture makes him look. My gelding that was by Cee’s Tizzy was quite thick and had a lot of substance. Many people also did not think he was a TB/pure TB. So a horse of this build being a TB, doesn’t really surprise me. I’ve also seen a fair amount of variation in the breed, especially once they fill out and/or get into a non racing career.
As a side note, I’ve seen a few draft (usually Percheron) x TB’s that were quite nice.