All leather has tannins or chemicals of some kind left in it. that's what makes it leather, instead of rawhide, and keeps it from rotting.
As a result, all leather can possibly have some kind of corrosive effect on metal. That is why it is not advisable to us your leather holster or knife sheath for storage (particularly with unblued non stainless steel)
As far as El Paso Saddlery, I have a buddy who swears by their stuff, so does his dad.
Eli W.