(ETA May 2013: After reading James' Sprang Unsprung, I've found that the fabric on the pots is created with free ends over a form and not with a warp stretched on a loom, so while the cloth may have the same structure as sprang it does not meet the generally accepted definition of sprang which is based on the method of working not the structure.)
I searched and found an interview of Goltz by Lakeland Public Television (YouTube user LakelandPTV), part of the footage for their one hour documentary Birchbark Canoe which is also on YouTube.
Here's an extract I transcribed that resonates with me as a handspinner. Not that it's about yarn or spindles at all and not that I spin replica yarn. It's more about an approach.
The whole area of past cultures and past technologies is something we’ve been really interested in. I’ve tried a lot of it. If you’re going to understand how people lived and functioned back a long time ago, it helps to immerse yourself in their technology and get some idea how it actually functions. So we’ve done a lot of that….You hear people talking almost in a negative way about things being primitive or old-fashioned or whatever, but when you think about it and you look at what people actually did in the past, it is very sophisticated. Like the canoes for one thing. When the Europeans came over and started the fur trade they had perfectly adequate boats. They didn’t use them. They used the birch bark canoe. Why? Because it was a much better watercraft for what they were doing. Enabled them to get around, it was reparable, it was lightweight, and it functioned very well. Much better than the big heavy wooden boats that they brought over.
A lot of the other things, the older technologies, for example the ceramics, the pottery that people made, when the fur trade came, a lot of the native people just quit making those because they got the trade kettles and the copper kettles and brass kettles and so on. I’ve made the clay pots and I’ve used them and cooked with them and did everything you can imagine you’d do with them, and actually from a functional standpoint they’re far superior to the European goods that were brought over. They’re just a little more work to make and if you drop them they break. That’s really the only advantage to the trade kettles that came over. And the fact that people didn’t have to make their own pots and kettles freed up their time to do other things. As far as cooking in those clay pots, man, in terms of thinking of something as being primitive, the old-style clay pots, I could put those on a gas kitchen stove and cook in them on an open flame on a gas stove–we had to invent Corningware before we could do that. Because ceramics that we make, you can’t do that with. But these older clay pots, they function just perfectly.
…People can sit and say I’m doing all these cool things but none of the stuff I do is me. It originates…we do a lot of things…I borrow from other cultures. Like with the canoes, that’s not my culture, my tradition. I do it, I’m interested in it, and I want to learn, and I want to learn so I can pass that information back to people that have lost it. One thing we do, with most of the things we do, and I guess I can use the canoes as an example, we don’t build a generic birch bark canoe. There are all kinds of regional styles, techniques, shapes, sizes, ways of putting these craft together, and we try to respect those traditions and those ways of doing things.