Actually "Pastel Cinnamon" is NOT another name for Pewter. It's the original full name for what now is often just called "Cinnamon".
Greg Graziani, they guy who produced the first Pastel Jungles (I think the name may have actually come from NERD but now they are commonly called just "Pastels"
later had a founding cinnamon animal. Before he proved the Cinnamon genetic he had on his web site a detailed comparison showing similarities it had to Pastel Jungle which was already proven genetic by that time. I suppose the point was that the Cinnamon had a "co-dominant look" but he also named it Cinnamon Pastel which provided a further link with Pastel Jungle. Similarities included white bellies, softened pastel hues, and I think also some head pattern and eye details.
Then he combined the two and produced the striking looking Pewter. With the similarities in traits, names, and unexpected synergy of the mutations when combined I was thinking it might turn out that they where alleles, different versions of the same gene. However, subsequent breedings have shown that an animal can have more than two copies total of the Pastel Jungle and Cinnamon Pastel genes combined which proves that they are at different locations.
So, Cinnamon Pastel is just the longer original name for Cinnamon and not the name of the combination with Jungle Pastel. The double het combo is Pewter. If you really want to get confused we can get into the names for the various 3 and 4 mutant allele combos including the Cinnamon Pastel, Black Pastel, and Pastel Jungle mutations. I have to look those up every time.