Why This is Rare
Of all of the possible Maltipoo colors, this is one of the most rare, seen even less often than a brown. In fact, the red Maltipoo and the black are the 2 most difficult colors to achieve when breeding.
The Maltipoo is a result of a direct breeding between a purebred toy Poodle and a purebred Maltese. Since the Maltese is a pure white dog, those genes will almost always affect the coloring of the puppies.
Now, the toy Poodle comes in a variety of colors...11 solids and 17 parti-colors (meaning a combination of 2 or more). In the process of breeding, any one of those color will almost always be influenced by the white gene.
Therefore, a brown will usually be diluted (faded) and the pups will be light tan, etc.
So, in regard to coat, you will generally find faded down colors.