This is true but it is not as close as breeders will linebreed. Breeders who linebreed will breed sibling to sibling, parent to offspring, grandparent to grandoffspring, uncle to niece and so on. It is very close relations and if you think about it, it has to be because they have these chams and they have a very short breeding life (a year and a half or so?) so anything beyond parent to offspring may be pushing it and I would assume that the male will be the elder.
Good breeders keep good records and know where their animals come from. They make a point to make it public knowledge and you should always ask them about a specific animal and it's background if you are interested in buying it for breeding. I think that once the animals are second cousins or farther, then it is a moot point and not really inbreeding at that point. Linebreeding denotes a more direct relation and once you get past a certain point, two individuals, though their ancestry may come back to one cham, will barely have any genetic material in common- it all dilutes by half over each generation so it barely takes time for each animal to only have say 5% lineage of the common ancestor. I would not consider this linebreeding.
Does that make sense?