This is a typical reaction of a bureaucracy with no answers, needing to be seen to being doing something. Even if the something is counterproductive and even stupid. As has been said above, a jumpseat occupant is a positive asset to security, unless the spouse is a terrorist. But if the spouse is a terrorist, chances are so is the pilot!
The facts don't matter too much to these people, they suffer from a "jobsworth" mentality. It is just unfortunate that they seem to permeate to positions with the power to instigate their stupid ideas without thought to the inconvenience of the masses.
Let us hope that the CAA have the sense to limit these restrictions to US bound flights only.