It's possible. Another factor is simply how air-tight the seals are. My older fountain pens tend to dry out faster than most modern ones. There are also some pens (Platinum 3776 for example) which are designed to virtually never dry out.

Possibly, but I've used Noodler's ink in them and it doesn't dry up either. (I left one sitting for nearly a year and started hard but would otherwise write fine. Back to normal after I cleaned it.) I suspect it may be the feed they have.