There was a few titanium ones made by lone star. Klaus made A few I think, for his own use.
The factory already made their chassis parts out of 4130 chromoly, a great upgrade over the common steel and cast aluminum other brands use. The only real upgrade from it is titanium. Which is even debatable in its own as people don’t understand that a chassis flexes on its own, more than you would think, titanium flexes different and can change the harshness of the entire machine. People seem to just see titanium and think it’s super cool because if it’s rarity and price.
To answer your question, no aftermarket frames have been produced and sold as an “add to cart” item.
Put a magnet on it. If it’s magnetic it’s either steel or chromoly steel. Meaning I’m 99.999999999% sure it’s an OEM frame.
I’m willing to bet this guys giving you the go-around or he has a gusset kit installed to strengthen the frame.
As YWF said the only ones I ever saw were the super rare full Ti frames. Other than that a few gusset kits. The factory frame uses a semi-square tube design with heavily rounded corners. The front part where the tubes come together and the front bumper mounts has a cast steel part. There are some aftermarket chromoly subframes if that's what he means. The stock subframes are aluminum.