I saw the check and immediately thought sportcoat. The flap pockets do seem to contradict that. That fabric would be a pretty bold for a suit, not that I'm averse to that myself.
There are degrees of casualness with a sportcoat: a navy blazer would be more suited to stronger shoulders than a corduroy like I'm wearing above. Though you're right that the flap pockets make this sportcoat not very casual at all.
I grabbed this sportcoat because I thought the more formal construction (structured shoulders, flap pockets) made contextual sense with the heavy tweed--I wanted an English country aesthetic. Others have commented that they wished the shoulders were less structured (there's actually not much padding at all due to the very thick fabric). Most of my flannels and all of the rest of my tweeds have soft shoulders, but I like having a variety of constructions in my jacket wardrobe, and in this case I think the structure makes sense.