I didn't know they offered this option, it's been done very well too! When you have a guilloche fileworked backspring slight gaps may be inevitable, can't say I've noticed any on mine though.
I have a very high opinion of Fontenille-Pataud, both their knives and customer service. You get really good knives that have a vast amount of handle options and sizes/styles of Laguiole. The thickness of the handles, as herisson noted, is very important too, it adds yet more appeal. Carbon and Damascus can be chosen, as well as matte or polished(crocus level, they use buffalo hide buffers!) I have three lockback Laguioles in bone,walnut and Ram's Horn, I hope to add a blonde horn version some time next year.
I'm carrying an old David today, its carbon is amazingly sharp, a good knife with much character but far off Fontenille-Pataud in finish and fit!
Superb knives with a nice carry pouch too.
Regards, Will