Yes, by wording, it is true. But we are rational beings...cant we apply some common sense? A fighter casting spells more accurately than a caster?
"Common Sense" on these boards is often illogical, and has little to do with what makes sense, nor with beliefs that are common.
The character in question would be a multiclass fighter that has developed ways to suppliment his weapon techniques with spell casting prowess.
Multiclassing does not imply that you can't use your class features with your new powers; quite the opposite, it implies that your new powers should be selected in a way to dovetail nicely with your class features.
Also, what if the fighter multiclassed into Swordmage, Warden, Battlemind or Paladin? Your common sense would go... don't see a problem here.
But then, there IS a problem, because by your -logic- the fighter is casting spells better than a caster. Or evocations, disciplines, or prayers.
In a game where the only non-casters are fighters, rogues, rangers, and warlords, and the fighter has an accuracy bonus, they already by default are more accurate than casters... and that accuracy bonus is not restricted to martial powers.
Of course, that's if you're not playing in a game setting where the martial power source runs similar to how swordplay works in wuxia films....
Look at how errata is unfolding. There is plenty to suggest that fighter bonus applying to implements is just errata waiting to happen.
RAW is not the same as Rules-as-Madame-Cleo-Predicts-Them-To-Be.
Speculation is good, but it is not useful for interpreting game rules as they are now.