The forum member from the UK with the Lutino said the original mutation was in a fawn, which I believe is called a Rubino, and he got his shadows from that.
I assume the first lutino's would have been used extensively and passed around that non extension gene.
One of my very well bred American Chinchilla does carries it and had a magpie when accientally bred to a Mini Lop so it can hide quite effectively.