Yeah, I think the standards must be different here. I don't blame Kap industries at all, I knew I was taking a bit of a risk.
I was seriously considering chopping part of the extinguisher handle off, or buying a white "kitchen" extinguisher (they seem to have smaller handles), but I think keeping it in a tool bag in the rear foot well will offer me more versatility. Then I'll have full motion of both front seats, and If I do ever have a rear passenger, I can chuck the bag in the trunk.
If the seats don't have full motion it's always a risk bringing the car in for detailing or service. Someone could unknowingly move the seat forward and ram it into the extinguisher.