I agree with the consensus. The feat says "You gain a +1 bonus on all attack rolls you make using the selected weapon." The first stage of a grapple is an attack roll. This is where the feat gives you the bonus. A grapple check is not an attack roll. To allow the feat to give you a bonus in the attack roll AND in the grapple check is to allow it to do double duty. That isn't how the feat was intended to work, so I would not allow the Weapon Focus feat to add to the grapple check. Why else would there be an Improved Grapple feat? Improved Grapple is where the grapple check bonus comes into play, and that's how a grappler improved his or her grapple check.
At least, that's my opinion. YMMV.
Hope this helps,
Flynn