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Yes, you're right, from directly in front the outer portion of the tire is exposed. That's intentional, and in line with what you see on OE deflectors. The underbody, especially the front, is a high-pressure zone, so that as air approaches it will want to escape out the sides, hence the direction of the airflow coming at the front tires is more like what you see in the second picture. Deflectors that extended to the outer edge of the tire profile would be diverting air further out than necessary, effectively increasing the frontal area of the car as a whole.
On production cars with deflectors you see a variation in how far to the sides the deflectors extend. This is almost certainly because every car will be different as far as the precise direction and pressure of the airflow as it approaches the front tires. It's pretty hard to tell w/o a windtunnel, though tuft testing might reveal something, but in my estimation my car will create more than average pressure in the front underbody, and therefore a greater angle at which air comes at the tires (say 35-40˚). My reason for suspecting this is that the lower edge of the bumper is quite high in comparison to the ground clearance, so the angle of my front undertray is quite steep. I wish there was an easy way to remedy this, but it would be challenging and impractical for a number of reasons, not least of which is the steep approach to many of the driveways I frequently use and my soft suspension--I need that ground clearance.
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